CARBENE-CAREENE REARRANGEMENTS: EVIDENCE
FOR A CYCLOPROPENE INTERMEDIATE
By
THOMAS TYLER COBURN
A DISSERTATION PRESENTED TO THE GRADUATE
COUNCIL OF THE UNIVERSITY OF FLORIDA IN PARTIAL
FULFILLMENT OF THE REQUIREI-IENTS FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY
UNIVERSITY OF FLORIDA
1973
ACKNOVJLEDGEMEKTS
The author wishes to express his appreciation to
Professor William M. Jones for the assistance and direction
he offered during the course of this work. Dr. Jones'
contribution as an excellent teacher and as a personal
friend cannot be stated adequately. Advice, assistance,
and experience extended by fellow members of the research
group, especially Kenneth Krajca, Russell LaBar, and
John Mykytka, are gratefully acknowledged.
The author also acknowledges v/ith appreciation the
enthusiastic support and good humor of his wife, Susan, and
children, Matthew and Katherine, while on their "Florida
Vacation" during which time this v;ork v;as accomplished.
Financial assistance provided by a National Science
Foundation Science Faculty Fellov/ship and a University of
Florida Graduate Council Fellowship made the work possible
and is gratefully acknowledged.
11
TABLE OF CONTENTS
Page
ACKNOWLEDGEI-IENTS ii
LIST OF TABLES vi i
LIST OF FIGURES viii
ABSTRACT jLx
INTRODUCTION 1
CHAPTER
I. A Norcaradiene-Bisnorcaradiene 7
II. Destabilization of the Cyclopropene Interme-
diate: Carbene-Carbene Rearrangements in the
Acenaphthylcarbene-Phenalenylidene System 13
III. The Precursor to a Stabilized Cyclopropene
Intermediate: Dibenzo [a, c] cycloheptatrienyli-
dene; A Comparison of Its Properties with
Those of Less Stabilized Intermediates 20
CONCLUSION 59
EXPERIMENTAL 65
General g5
Acenaphthylene-1-carboxaldehyde (20^) 67
7,7-Dichlorodibenzo [a,c]bicyclo [4.1.0]heptane (34^)... 68
6-Chloro-5tf-dibenzo [cj c7]cyclohepten-5-ol (3_5) 69
6-Chloro-5A'-dibenzo [a,c;] cyclohepten-5-one (36) 70
6-Chloro-6 , 7-dihydro-5//-dibenzo [a^o] cyclohepten-
5-one (37_) 70
6,7-Dihydro-5/?-dibenzo [a,c]cyclohepten-5-one (39) 72
111
Page
Mixtures of 6-Chloro-6 ,7-dihydro-5^-diben70 [a^ e]-
cycloh.epten-5-one {32) and 6 ,7-Dihydro--5A'-
dibenzo [a, e]cyclohepten-5-one (39^) from
Catalytic Reduction 73
5Z?-Diben20 [a^ a]cyclohepten-5-one (38j 73
Preparation of Tosylhydrazones 7 4
Preparation of Sodium Salts of Tosylhydrazones 75
Thermolysis and Photolysis of Aldehyde and Kf^tone
Tosylhydrazone Sodium Salts 76
Preparative-scale Photolysis of Diazo-2 , 3 , 4 , 5-
tetraphenylcyclopentadiene in Benzene at
lOQO 77
Small-scale Photolysis of Diazo-2 , 3 ,4 , 5-tetra-
phenylcyclopentadiene in Benzene at 100° 78
Pyrolysis of Tropone Tosylhydrazone Sodium Salt
in the Presence of 2 ,3 , 4 , S-Tetraphcnyl-
cyclopentadienone 79
Photolysis of 1,2 ,3 ,4-Tetraphenyl-7i:/-benzocyclo-
heptene (9^) and 5 , 6 ,7 , 8-Tetraphenyl-7 /-
benzocycloheptene (10^) 79
Room Temperature Photolysis of Diazo-2 , 3 , 4 , 5-Tetra-
phenylcyclopentadiene in Benzene 80
Pyrolysis of Phenalen-1-one Tosylhydrazone Sodium
Salt (_19 ' ) in Dioxane 80
Pyrolysis of Acenaphthylene-1-carboxaldehyde Tosyl-
hydrazone Sodium Salt (21^') in Dioxane 82
"Hot Tube" Pyrolysis of Phenalen-1-one Tosyl-
hydrazone Sodium Salt (19^' ) 83
"Hot Tube" Pyrolysis of Phenalen-1-one Benzene-
sulfonylhydrazone Sodium Salt 84
"Hot Tube" Pyrolysis of Acenaphthylene-1-carbox-
aldehyde Tosylhydrazone Sodium Salt i21_' ) 85
9- (2,4 ,6-Cycloheptatrien-l-yl)phenanthrene (£2) .
86
IV
Page
Low Temperature Photolysis of 5 "-Dibenzo [a, c]-
cyclohepten-5-one Tosylhydrazone Sodium
Salt (£1 ' ) in Tetrahydrof uran 88
Low Temperature Photolysis of the Sodium Salt of
5//-Dibenzo [a, c?]cyclohepten-5-one Tosylhydra-
zone (4_1 ' ) in the Presence of Styrene 88
Low Temperature Photolysis of the Sodium Salt of
5//-Dibenzo [a^ c7]cyclohepten-5-one Tosylhydra-
zone (£1') in the Presence of Dimethyl
Fumarate 89
Low Temperature Photolysis of 5^-Dibenzo [a, c]-
cyclohepten-5-one Tosylhydrazone Sodium Salt
(£1') in the Presence of 1 , 3-Cyclopentadiene. . . 89
Low Temperature Photolysis of 5//-Dibenzo [a, c] cyclo-
hepten-5-one Tosylhydrazone Sodium Salt (41*)
with Subsequent Addition of 1 , 3-Cyclopentadiene 90
Generation of Dibenzo [a^ c] cycloheptatrienylidene
(32) in the Presence of Furan 91
Photolysis of 1,7- (o-Biphenylenyl) -endo-2, 5-epoxy-
norcar-3-ene (4_4) 93
Pyrolysis of 1 ,7- (o-Biphenylenyl) -e^^do-2 , 5-epoxy-
norcar-3-ene ( 4_4 ) in Benzene 94
Pyrolysis of 5£?-Dibenzo [a, c] cyclohepten-5-one
Tosylhydrazone Sodium Salt {4_1 ' ) in the
Presence of 2 , 3 ,4 , 5-Tetraphenylcyclopenta-
dienone 95
Thermal Rearrangement of 10 , 11 , 12 , 13-Tetraphenyl-
9//-Cyclohepta [ ^ phenanthrene (£6) 96
Low Temperature Photolysis of 4 , S-Bonzotropone
Tosylhydrazone Sodium Salt (5_3 ' ) in the
Presence of 1, 3-Cyclopentadiene 97
2 7 2 8
Pyrolysis of e«do-5 , 6-Benzotetracyclo [7 . 2 . 1. 0 ' .0 ' ]-
dodeca-3,5,10-triene (£8) 98
Low Temperature Photolysis of 3 , 4-Benzotropone
Tosylhydrazone Sodium Salt (S^' ) in the
Presence of 1 , 3-Butadiene 98
Page
Low Temperature Photolysis of l-Vinyl-6 , 7-benzo-
spiro[2.6]nona-4,6,8-triene (50) 100
Pyrolysis of 4 ,5-Benzotropone Tosylhydrazone Sodium
Salt (53^') in the Presence of 2 , 3 , 4 , 5-Tetra-
pheny Icyclopentadienone , 101
Pyrolysis of Tropone Tosylhydrazone Sodium Salt
in Furan 103
Generation of Phenanthrylcarbene (32) in the
Presence of Furan 104
Low Temperature Photolysis of the Sodium Salt of
5ff-Dibenzo [a, c] cyclohepten-5-one Tosylhydra-
zone (4]^') in the Presence of Diethylamine. . . . 106
Photolysis of Phenyl Azide in the Presence of
Butylamine 106
Photolysis of Phenyl Azide in the Presence of
Furan 108
REFERENCES 109
BIOGRAPHICAL SKETCH 115
VI
Table
LIST OF TADLtS
Page
1 Solvent Effect on the Reduction of 6-Chloro-
5//-dibenzo [a,c]cyclohepten-5-onc (3£) 24
2 Nmr Spectral Properties of £6 and Similar
Compounds 33
3 Nmr Spectra (t) 4 2
4 H-nmr (t) 42
5 Nmr Spectral Properties of 50 and Similar
Compounds 45
6 Hydrocarbons from Reactions with Tetracyclone. . 49
7 Effect of Added Shift Reagent on H-nmr Spectra
of Adduct 4_4 92
8 Effect of Added Shift Reagent on "^H-nmr Spectra
of Adduct 57^ 104
Vll
LIST OF FIGURES
Figure Page
1 Mechanisms of Rearrangement 2
2 Isomerization of 3-Naphthylcarbene 5
3 A Mechanistic Hypothesis 8
A Delocalization Energies 21
5 Synthetic Scheme 23
6a Nmr Spectra of 3^9 25
6b Nmr Spectra of 3_7 26
7 Nmr Spectra of 4_4_ with Increasing Amounts
of Eu(fod)3 Present 34
8 H-nrar Spectra of Adducts 44
9 A Two-step Mechanism for Adduct Formation 46
10 H-nmr Spectra of _57 with Increasing Amounts
of Eu(fod)3 Present 52
Vlll
Abstract of Dissertation Presented to the
Graduate Council of the University of Florida in
Partial Fulfillment of the Requirements for the
Degree of Doctor of Philosophy
CARBENE-CARBE1:E REARRANGEr^NTS : EVIDENCE FOR
A CYCLOPROPENE INTERMEDIATE
BY
Thomas Tyler Coburn
August, 1973
Chairman: V7illiara M. Jones
Major Department; Chemistry
Evidence is presented that implicates a fused cyclo-
propene intermediate in the interconversion of aromatic
carbenes and arylcarbenes. A carbene potentially capable of
rearrangement with the requisite fused cyclopropene inter-
mediate incorporated into an annelated bicyclo [3 . 1. 0] hex-6-
ene structure (acenaphthylcarbene) is sufficiently strained
to avoid rearrangement in solution, although gas phase
isomerization (410°) still occurs. When the required
rearrangement intermediate has an annelated bicyclo [4 . 1. 0] -
hept-7-ene structure (dibenzo [a, c] cycloheptacrienylidene) ,
rearrangement takes place readily in solution at room tempera-
ture and below. Annelated cycloheptatrienylidenes in which
the loss in resonance energy accompanying cyclopropene forma-
ix
tion is minimized to the greatest extent are most susceptible
to reorganization. In the case of unsymmetrical carbenes ,
the direction of rearrangement is controlled by the relative
stabilities of the two potential cyclopropene intermediates.
A convenient, high yield synthesis of 5ff-dibenzo-
[a,£;]cyclohepten-5-one is developed, and the properties of
dibenzo[a,c?]cycloheptatrienylidene are examined. Dibenzo-
[a,c]cycloheptatrienylidene and 4 ,5-benzocycloheptatrienylidene
rearrange rapidly in solution, and when the rearrangements
take place in the presence of dienes, Diels-Alder adducts of
the cyclopropene intermediates are obtained. The structure
of these adducts can be deduced from a comparison of their
•^H-nmr spectral properties with those of model compounds
previously characterized. The molecular geometry of the
single furan adduct of dibenzo [a, c] cycloheptatrienylidene is
determined from an analysis of lanthanide- induce proton nmr
shifts. Both carbenes react with cyclopentadiene to yield
only the endo-anti isomer expected to result from cycloaddi-
tion of 3-monosubstituted cyclopropenes with this diene.
Furan adducts are obtained under both thermal (125 )
and photochemical (30° and -60°) conditions. Tetracyclone
adducts result from thermal generation of the carbenes, and
cyclopentadiene and butadiene adducts are obtained from low
temperature (-60°) reactions of the cyclopropene intermediate
which forms from the photolytically generated carbene. The
adducts are shown not to be secondary photo-products, and
a two step thermal process is ruled out. Also, irreversible
X
cyclopropene formation competitive with rearrangement is
Shown to be an unsatisfactory explanation of the experimental
results.
Cyoloheptatrienylidene, which has been previously
Shown not to rearrange in solution, reacts with dienes to
give adducts that apparently result from a two step process.
The thermal reaction of cyoloheptatrienylidene with tetra-
cyclone offers no conclusive evidence that cyclopropene trap-
ping occurs. Although the f uran-cycloheptatrienylidene
adduct has the correct gross structure for formation by
cyclopropene trapping, an endo transition state would be
demanded. Since dibenzo la, .Icycloheptatrienylidene reacts
with furan via an e.o transition state and since steric and
secondary orbital effects fail to indicate any reason for .
the differing modes of cycloaddition, a two step mechanism
for the cyoloheptatrienylidene reaction is suggested.
Phenanthryloarbene, which does not ring expand in
solution, fails to give any indication of cyclopropene
formation when generated in solutions containing dienes.
Phenylnitrene also fails to react with furan although it is
known to rearrange in solution. Although there is no
assurance that this diene is adequate for 2H-a.irine trap-
ping, the possibility that nitrenes rearrange via a Wolff- _
type mechanism rather than through 2«-azirine intermediates
is discussed. The information these cyclopropene trapping
experiments prov.de in understanding the mechanism of carbene-
4.,, -.r.^ 1-h*^ fTPneralitv of these conclusions
carbene rearrangements and the generaxii^y
is analyzed.
XI
INTRODUCTION
Unlike other reactive intermediates which are highly
susceptible to rearrangement, carbenes generally undergo
intra- or intermolecular abstraction, insertion, or addition
reactions rather than conversion to isomeric carbenes of
greater stability. The rearrangement of aromatic carbenes
to arylcarbenes (and the reverse reaction) is a notable
exception to this generality. Besides detailed studies
concerned with the conversion of phenylcarbene (1^) and its
derivatives to cycloheptatrienylidenes (2^) in the gas
phase and of benzocycloheptatrienylidene (3) to naphthyl-
1 2
carbene (£) in solution, ' a growing number of hetero-
cyclic ' and nonbenzenoid carbenes have been shown to
undergo isomerization. Yet the mechanism of this reorgani-
zation remains a subject of considerable conjecture. Some
suggested mechanistic alternatives are collected in Figure 1.
A cyclopropene intermediate (5^) (Figure la) has been
widely assumed. ~ This mode of rearrangement is suggested
by the v.'ell known synthesis of cyclopropenes from vinyl-
carbenes. However, the strain in such a bicyclic struc-
ture may be sufficient to prevent its intermediacy , making
a concerted rearrangement via a cyclopropene-like transition
2 10
state (Figure lb) a reasonable alternative. ' Also, isomeri-
zation of an aromatic carbene to the cyclopropene 5^ may be
Mechanisms of Rearrangement
a)
b)
•CH
Ji:^
V
1
c)
_ii,
"sT
■^/H
•'CH
d)
-ik
•CH
Figure 1
vitiated by the conformational restrictions placed on the
carbene center. Such restrictions may be sufficient to
preclude the required favorable interaction of carbene
orbitals with the double bond.
A mechanism based on that of the Wolff Rearrangement —
actually a "retro-Wolff" mechanism for aromatic carbene to
arylcarbene isomerization (Figure Ic) — has also been sug-
gested.^' '' Products result from migration of a single
^-»'- "^ " R R
bonded a-substituent to the carbene center. This mechanism
when applied to the isomerization of arylcarbenes requires
a highly strained, cyclic, bent vinyl cation (6) , as a
4
distinct intermediate, or, as preferred by some workers, as
a transient stage along a concerted reaction profile. The
strain in this charge separated structure may be qualita-
tively similar to that in a cyclopropene intermediate or
transition state, but 6^ has one less a-bond than 5^.
Ring opened diradicals (7) (or charge separated species)
12
such as those postulated in nitrene rearrangements have
also been suggested (Figure Id) . ' The low temperature
12 5
employed for some rearrangements, ' ' the absence of
hydrogen abstraction products or other products from a
radical precursor when the rearrangement occurs in ether
1 2
solvents, ' and the dramatic acceleration of the reorgani-
1 2
zation on annelation, ' make a ring opening mechanism
unattractive .
other mechanistic proposals can be ruled out on
similar grounds and, in fact, appear even less likely.
For example, isomerization of the aromatic carbene to the
7-norcaradienylidene followed by a rearrangement such as
that suggested by Skattab^zJl for the vinylcyclopropylidene
13
to cyclopentenylidene reorganization appears quite
unlikely. Strict adherence to Skattab^l ' s process requires
7-norbornadienylidene as an intermediate that isomerizes
cleanly to the arylcarbene leaving no evidence of its
presence (even under conditions where products from both
aromatic and arylcarbenes are detected ) . There is no
precedent for this highly specific rearrangement of 7-
norbornadienylidene to phenylcarbene (1) , and to avoid the
necessity of this carbene an unusual multiple bond fission
of the tricyclopentane intermediate must occur. The
multiple bond forming reaction necessary for the reverse
reaction requires a startling coincidence of orbital inter-
action that boggles the imagination. Therefore, this
mechanistic possibility seems unworthy of detailed con-
sideration. Other examples of "unlikely" mechanisms include
those postulated for the isomerization of arylcarbenes.^'^
A number of these mechanisms have been previously eliminated
with labeling experiments, but such mechanisms are largely
inapplicable to the present discussion anyway since they
avoid the intermediacy of an aromatic carbene.
Indirect evidence that favors a cyclopropene inter-
mediate or transition state has been previously presented. ■^' ^ '-"-^
The cyclopropene mechanism (Figure la) differs from the
Wolff mechanism (Figure Ic) in the extent of double bond
character in the reacting bond. An experimental test of
bond order versus degree of bond migration employing
naphthylcarbenes showed exclusive migration of the bond of
higher order just as expected for a rearrangement proceeding
via cyclopropene (5b) formation (Figure 2a) . The mild
experimental conditions which permit contraction of benzo-
cycloheptatrienylidene {3) to naphthylcarbene (£) when com-
pared with those required for the phenylcarbene {1) to
cycloheptatrienylidene (2) reorganization argues against an
intermediate in which the aromaticity of the additional
aromatic ring is reduced [as occurs if the bond of lower
order migrates by a Wolff mechanism (Figure 2b) ] .
A) The Cyclopropene Mechanism:
Products
B) The Wolff Mechanism:
Products
4 6b 8
Isomerization of 3-Naphthylcarbene
Figure 2
Wentrup, Mayor, and Gleiter have recently criticized
the suitability of this indirect evidence as grounds for
4
dismissing the Wolff mechanism. They point out that the
bond of higher order may migrate by a Wolff mechanism in
order to avoid the high energy 3-benzocycloheptatrienyli-
dene intermediate 8^ that results from migration of the bond
of lower order. Examples of nitrene-carbene isomeriza-
tions and heterocyclic carbene rearrangements are offered
to support the contention that "ring expansions in aromatic
carbenes are largely determined by the energy differences
14
between the first reacting species and the product." The
mechanistic differences between nitrene-carbene rearrange-
ments and carbene-carbene rearrangements are more stricking
than the similarities. Thus, it is doubtful that mechanistic
conclusions extracted from analysis of nitrene isomeriza-
tions can necessarily be extended to carbon analogues.
Nevertheless, the need for more direct evidence pertaining
to the mechanistic question is clear.
CHAPTER I
A Norcaradiene-Bisnorcaradiene
Of those intermediates postulated, the cyclopropene 5^
seems most easily demonstrated if present since reactions
15
and properties of cyclopropenes are well understood, while
those of other potential intermediates are much more specu-
lative. Also, indirect evidence makes a cyclopropene 5^
appear to be the most likely intermediate ' so it seems
advisable to devise experiments aimed at detecting 5^.
The report by Mitsuhashi and Jones that cyclohepta-
trienylidene (2) reacts with 2,3 ,4 ,5-tetraphenylcyclopenta-
dienone (tetracyclone) to yield two 7//-ben2ocycloheptenes,
l,2,3,4-tetraphenyl-7fi-benzocycloheptene (9) and 5,6,7,8-
tetraphenyl-7ff-benzocycloheptene (IjO) is surprising since
17 18
Diirr and coworkers report ' generation of the same pro-
posed intermediates, 1,2 ,3 ,4-tetraphenyl-lafl-benzocycloheptene
(11) or its norcaradiene-bisnorcaradiene isomer (12^) , from
tetraphenylcyclopentadienylidene in benzene and obtain a
single product, 1 ,2 ,3 ,4-tetraphenyl-7ff-benzocycloheptene
(9) . If these reports are correct, an additional interme-
diate must be involved in the cycloheptatrienylidene reaction
that is inaccessible via the cyclopentadienylidene route.
A possible explanation is outlined in Figure 3. It requires
that the cycloheptatriene to norcaradiene-bisnorcaradiene
isomerization in this system be inopperative due to the much
more rapid occurance of a (1 . 5] -hydrogen shift. Although
such an hypothesis (norcarcidienc isomerization having a
19 20
higher activation energy tlian a (1.5]-s'nift ) is unpre-
cedented, rapid cycloheptatriene--norcaradiene equilibration
A Mechanistic Hypothesis
4>
- . Figure 3 . -
would demand identical products and product ratios regard-
less of the mode of entry into the equilibrating system.
If the cycloheptatricne to norcaradiene isomerization is
prevented by incorporation of the potential norcaradiene
into a norcaradiene-bisnorcaradiene skeleton, the direct
cycloheptatrienylidenc adduct to tetracyclone 15^ should fail
to isomerize to 14^ as well. Independent preparation of 15,
15 14_
siobjection of 15 to the reaction conditions, and isolation
of little or no 75-benzocycloheptene 10^ would be convincing
evidence for direct formation of 14 (and thus cyclopropene
trapping) in the cycloheptatrienylidene reaction with tetra-
cyclone.
Toward this end, the product ratios via the two routes
were checked under as nearly identical conditions of solvent
and temperature as possible. Tropone tosylhydrazone salt
was pyrolyzed in the presence of tetracyclone in a sealed
tube with benzene as solvent at 10015*^ (boiling water bath) ;
diazo-2 , 3 ,4 ,5-tetraphenylcyclopentadiene in benzene (sealed
tube) was photolyzed (550W, "Hanovia high pressure Hg vapor
lamp," Pyrex filter) at 100+5° (boiling water bath) for an
identical period of time. Products were quantitatively
determined by gas chromatography (5% SE-30, lO'xl/8", 235°C) ,
authentic samples of 1 ,2 , 3 , 4-tetraphGnyl-7^-benzocycloheptene
{9} and 5 ,6 , 7 ,8-tetraphenyl-7if-benzocycloheptene (!£) for
comparison being supplied by Mitsuhashi. A mixture of the
authentic materials was subjected to the thermolysis and
photolysis reaction conditions and the stability of these
products to reaction conditions demonstrated. Thus assurance
10
was obtained that the analysis procedure was truly indi-
cative of the ratio of products formed.
Contrary to expectations identical ratios of 9^:10
(1:4 i.olar ratio) resulted from the two reactions. There-
fore ..1 rapid cycloheptatriene — norcaradiene-bisnorcaradiene
equilibrium results, and no clue as to the point of entry
into the equilibrating system can be obtained from structures
of final products.
Although a proof of cyclopropene trapping is obviated,
these reactions offer entry into a series of very interesting
intermediates and products. Tetraphenylcyclopentadienylidene
addition to benzene gives as the major product 1,2,3,4,5-
pentaphenylcyclopentadiene (1£) along with the two 7^-benzo-
cycloheptenes £ and 10 (ratio of 16:9:10^; 47:10:43). This
confirms the proposal that an initially formed spiro-compound
18 21
gives IX thermally ' and the benzocycloheptenes (ll;;:rl2 ^13)
17 18
photolytically. ' High temperature photolysis at low
photo-efficiency (i.e., higher concentration of diazotetra-
4-
— 11
phenylcyclopentadiene and longer light path length of the
irradiating light) offers a synthetically useful method for
preparation of pentaphenylcyclopentadiene 16^. Photolysis of
the diazo starting material (0.50 g) in 40 ml benzene (sealed
11
tube, twice the diameter of that employed previously) for
6 hours gave after recrystallization (etlianol) 0.39 g (68%
yield) of the cyclopentadiene ]_6 (iTi.p. 248-252 , lit. '
244-246°, 247°, 254°) with spectral properties as reported.
The equilibrium constants for equilibration of the inter-
mediates 11^:^12 ^13 are expected to be influenced by both
substituents and temperature. Photolysis of the diazo
starting material in benzene at 30 gives the 7ff-benzocyclo-
heptenes 9_ and _1£ in a ratio of 1:1 v/ith no formation of
pentaphenylcyclopentadiene 16^. Thus temperature variation
permits remarkable control of the products formed in the
photochemical reaction.
The primary utility of these reactions is the access
they provide to the unique norcaradiene-bisnorcaradiene
intermediate 12^. Although there are at least tv/o other pos-
sible mechanisms that might be envisioned for interconversion
of the laff-benzocycloheptenes 1]^ and 13^ which by-pass 12 ,
neither would be expected to be competitive with either
20
[1.5] -hydrogen migration or the cycloheptatriene — norcara-
19
diene rearrangement which is known to be particularly facile
(E <10 Kcal/mole) . Thus, a concerted thermal [1 . 11] -sigma-
tropic rearrangement is forbidden (rearrangement must be
thermal even if it can also be photochemical since the
IjL ^12^^12 equilibration occurs in the absence of light when
entered via the cycloheptatrienylidene-tetracyclone reaction) .
Also, reversible ring opening to the severly crowded all
cis-cycloundecahexaene (either by a concerted or a diradical
12
mechanism but occurring with or without photolysis) that
could re-close to the rearranged product would hardly be
expected to occur at temperatures as low as room tempera-
ture.
The norcaradiene-bisnorcaradiene 1_2 is a particularly
intriguing molecule since it is not only capable of norcara-
diene — cycloheptatriene isomerization but possibly of an
unprecedented degenerate (without phenyl substituonts)
rearrangement as well. This rearrangement involves an
orbital symmetry allowed antara-antara [5. 5] -sigmatropic
rearrangement with cleavage of C-6,6' and formation of a new
sigma bond between carbons 2 and 2'. The molecular geometry
of 12 is particularly well suited for this isomerization to
H H
occur as a concerted rearrangement, particularly in light of
destabilization predicted for the [5 . 5] -spirarene formed by
23
hemolytic cleavage of C-6,6'. Unfortunately, the particular
substitution pattern of 1_2 does not allow detection of this
isomerization if it occurs. However, a number of substitu-
tion patterns that would permit detection can be devised.
CHAPTER II
Destabilization of the Cyclopropene Intermediate; Carbene-
Carbene Rearrangements in the Acenaphthylcarbene-Phenalenyli-
dene System
A carbene specifically designed with structural features
that destabilized a cyclopropene intermediate 5^ should behave
differently than a carbene with structural features that
stabilize this intermediate. In particular, the former
should be less prone to rearrangement if the cyclopropene _5
is truly an intermediate in these reorganizations. Were
the cyclopropene 5 sufficiently destabilized, the mechanism
of the rearrangement might be altered to avoid its inter-
mediacy .
One means of destabilizing this intermediate would be
to incorporate it into an abnormally small bicyclic system.
A bicyclo [3.1.0] hex-5-ene (for example, 5d) should be sub-
stantially more strained than the more usual bicyclo [4 . 1. 0] -
hept-6-ene (for example, 5a, 5b, or 5c) . Therefore, 1-ace-
^
5d 5a
13
14
naphthylcarbene (L?) and 1-phenalenylidone (1£) were chosen
for a study of the effect of straining the cyclopropene
intermediate, and how sucli dcstabilization influences the
isomerization of these caibenes. Initially the experimental
results left much to be desired due to the abnormal properties
of phenalenylidene (18^) and the small yield of carbone pro-
24
ducts detected. However, e recent report has detailed the
properties of carbene _18 and is compatible with these results.
Phenalen-1-one tosylhydrazono (19^) was prepared from
commercial phenalen-1-one (Aldrich) by the standard method
24 25
and had properties identical to those reported previously. '
Acenaphthylene-1-carboxaldchyde (20.) was synthesized from
2 6
acenaphthylene by the Vilsrixir-llack reaction. This alde-
hyde was obtained in 24% yield as a solid (m.p. 55.5-57 ,
26
contrary to the report that it is a liquid) which formed
a semicarbazone with m.p. 241-243 (lit., 240 ) and was
2 6
oxidized to 1,8-naphthalic anhydride in the reported manner.
Acenaphthylene-1-carboxaldehyde tosylhydrazone (21^) was
obtained in the standard way. Tosylhydrazones 19^ and 2_1
were converted to sodixom salts 19 ' and 21' with sodium
hydride employing a method similar to that described pre-
vxously.
Thermolysis of phenalen-1-one tosylhydrazone sodium
salt (19 ' ) in dioxane (sealed tube) at 160 produced
25
phenalen-1-one azine (22^) (ir, uv, tic identical to
24
authentic material) as reported by others. Hov;ever, 22_
was not completely stable to these reaction conditions and
15
24
its yield was irreproducible. Phenalene (22) (6.9%; uv,
97 28
nmr, gc, tic identical to authentic material ) was also
isolated along with a small quantity of previously undetected
29
peropyrene (Dibenzo [cJ^ Zm]perylene, 24_) (0.7%; uv-vis , gc,
tic identical with authentic material ) . Due to the carcino-
genic nature of peropyrene (2£) , this compound was not
isolated as the pure solid. Properties of dilute solutions
left little doiobt as to the identity of 2£. Yields were
29
determined by uv-vis spectrophotometry in benzene.
NTs
160'
Dioxane
19
22
23
24
Thermolysis of acenaphthylene-1-carboxaldehyde tosyl-
hydrazone sodium salt (21 ' ) under conditions similar to
those employed for generation of phenalenylidene (1£) gave
about 50% nitrogen evolution and 75-acenaphtho [1 , 2-c] pyrazole
(25) (m.p. 238-241°, lit.,^^ 239°) as the major product.
1-Methylacenaphthylene (26^) (7%, identical with authentic
33
material by uv and mass spectrometry) and a compound tenta-
tively identified (nmr) as the dioxane insertion product of
acenaphthylcarbene (27_) (~3%) were also isolated. No trace
of any common product could be detected by gas chromatography
of the two reaction mixtures.
16
CHNNTS
16 Q^
Dioxane
ii' 25 26 27
Hot tube pyrolysis under the conditions employed for
isomerization of phenylcarbene (_1) to cycloheptatricnyli-
dene (2^) successfully effected rearrangement of the aryl-
carbene 11_ to phenalenylidene (18^) as evidenced by detection
of peropyrene (24^) and phenalene (23) in product mixtures.
In fact, 22 and 2A_ were the major volatile products from hot
tube pyrolysis of acenaphthylene-1-carboxaldehyde tosylhydra-
zone sodium salt (21_;_) at 410° (5.3% 24^, 3.2% 22, 1.8% 26
detected) .
No acenaphthylcarbene products such as 26^ were obtained
from hot tube pyrolysis of phenalenylidene (1£) (limit of
detection 0.01% by gc) . Unfortunately, reported yields from
hot tube pyrolysis experiments may not be particularly infor-
mative since the low volatility of 2A may have resulted in
some condensation prior to the trap. To avoid contact with
24 , this possibility was not experimentally tested. Hot
tube thermolysis of phenalen-1-one tosylhydrazone sodium
salt (19' ) at 410 gave peropyrene 24_ and phenalene 22 as
major volatile products along with a trace of 2,3-dihydro-
phenalene 28^, identified by preparative gas chromatography
28
followed by uv and mass spectrometry (3.8% 24./ 0-5% 23,
0.05% 22 detected). Isolation of 2 ,3-dihydrophenalene (28)
17
indicates a strongly reductive environment in the pyrolysis
17
410
o
24
23
26
18
410
o
24
23
28
tube which may possibly be due to the transient presence of
dihydroperopyrene (29) (a logical precursor of peropyrene) .
In addition, gas chromatography of both pyrolysis product
mixtures shows products from sodixim p-toluenesulf inate at
various stages of reduction (thiocresol and tolyl disulfide
detected by coinjection and minor components noted from the
change in the chromatogram when the benzenesulfonylhydrazone
salt of phenalen-1-one was pyrolyzed in place of 19' ) .
The origin of peropyrene (24^) (or its precursor 29_) is
not clear at this time. It could reasonably originate from
34
either the carbene dimer 30^ or the known disproportiona-
tion of the phenalenyl radical 31^ (a logical precursor of
phenalene 22) • In either event, it is apparent that
acenaphthylcarbene (17) undergoes carbene-carbene rearrange-
18
men
t to phcnalcnylidene (1£) . In spite of the additional
(+H)
18
31
(-H)
30
29
Oxidation
24
strain on the cyclopropene intermediate 5d^ the rearrange-
ment still occurs — this rearrangement being unique in that
it is the first example of such an isomerization requiring
expansion of a five-member ring. This result reinforces
the previous indirect evidence implicating a cyclopropene
intermediate since migration of only C-2 occurs (i.e., inser-
tion is into the bond of higher ir-bond order, or a preferable
statement might be that the products result only from the
more stable of the two possible cyclopropene intermediates
or transition states) . There is clearly no evidence for an
obvious variation in the mechanism of rearrangement.
The comparable conditions for the rearrangement of
acenaphthylcarbene {11) to phenalenylidene (18^) and of
phenylcarbene (1) to cycloheptatrienylidene (2^) suggests
that the lesser loss in resonance energy accompanying forma-
19
tion of the cyclopropene 5d (compared v.'ith formation of 5a)
partially offsets the additional strain. However, the strain
in 5d is apparently sufficient to prevent rearrangement in
solution from being competitive v/ith intermolecular processes,
This is particularly pertinent since luethano-lOir-annulenyl-
carbene in which the cyclopropene intermediate 5e is incor-
porated into a much larger fused ring system undergoes
5e
rearrangement readily in solution. Thus these results are
completely consistent with rearrangement via a cyclopropene
intermediate or transition state.
CHAPTER III
The Precursor to a Stabilized Cyclopropene Intermediate;
Dibenzo [g, g] cycloheptatrienylidene; A Comparison of Its
Properties with Those of Less Stabilized Intermediates
The most acceptable evidence for a cyclopropene inter-
mediate 5^ in a carbene-carbene rearrangement would be direct
observation of this intermediate, or lacking that, trapping
of the short lived species. With the observation of high
12 5
yield rearrangements that occur in solution, ' ' experiments
with this aim were indicated. The cyclopropene, 5a, and the
two carbenes, 1 and 2^, have been estimated to be of similar
9
energy. However, it seems advantageous to choose carbenes
interconvertible via an intermediate having the maximum
energetic advantage (or, minimum energetic disadvantage)
possible. The dibenzo [a, c] cycloheptatrienylidene-phenanthryl-
carbene system was chosen since the intermediate, 5_c, was
expected to form with the least loss in resonance energy.
Figure 4 gives an indication of the loss in resonance energy
as the cyclopropene intermediate is formed from the aryl-
carbene or from the aromatic carbene. The resonance energy
of the carbenes is taken to be equal to that of the respec-
tive cations, and the resonance energy of the intermediate
is taken to be equal to that of the linear polyene with
appropriate annelation. Delocalization energies are simple
20
Delocalization Energies
21
(-1.73276)
(-2.00006)
.,-
DE= 2.72066
5a
DE= 0.987 9 6
DE= 2.98796
CH
(-1.49486)
(-1.77196)
DE= 4.42696
5b
DE= 2.93216
(-^ .AiOf^R)
23
DE= 6.26166
(-1.64566)
DE= 4.70406
32^
DE= 6.46646
35
DE= 4.82086
Figure 4 : y.-sc-
HMO values taken from Streitwieser ' s compilations.""' Only
differences between the three series are of significance.
The advantage of choosing dibenzo [a, c] cycloheptatrienylidene
(32) is obvious. Reactive dienes are expected to be appro-
priate trapping reagents for the strained cyclopropene 5c.
Although dibenzolajd] cycloheptatrienylidene has been
previously studied and found to behave as a diarylcarbene
with no tendency to rearrange in solution, dibenzo [a^ c] -
cycloheptatrienylidene 32_ has not previously been reported.
The preparation of this carbene and some of its reactions
with particular attention to the similarities and differences
22
between carbene _32 an<3 cycloheptatrienylidene 2 and 4,5-
benzocycloheptatrienylidene 3^, and the behavior of these
carbenes in the presence of dienes were examined for the
implication of a cyclopropene intermediate.
5tf-Dibenzo [a, c] cyclohepten-5-one {_38) was required for
the preparation of the carbene 32- Prior methods of synthe-
37 38
sis ' appeared too troublesome or expensive. Therefore,
a synthetic sequence (Figure 5) based on a method for prepara-
tion of 6-chloro-5//-dibenzo [a,c?] cycloheptene previously
39
developed by Waali and Jones was employed. A procedure
similar to that reported by Joshi , Singh, and Pande
allowed the accumulation of a large quantity of 7 ,7-dichloro-
diben2o [a,c?]bicyclo [4 . 1. 0] heptane (3_£) . The alcohol 35 was
obtained in quantitative yield by heating a melt at 170° for
30 minutes, and then cooling and hydrolyzing the resultant
oil with aqueous acetonitrile containing sodium bicarbonate.
Isomerization of the alcohol 35^ to the chloroketone _r7 was
most conveniently accomplished by oxidation with activated
manganese dioxide to the unsaturated chloroketone 36 ""^^
(90?, yield) followed by catalytic reduction (78% yield) .
Hydrogenolysis accompanies hydrogenation. and occurs
especially rapidly in ethanol. In fact, catalytic reduction
of the unsaturated chloroketone _36 with two equivalents of
hydrogen in ethanol appears to be the method of choice for
synthesis of 6 , 7-dihydro-5ff-dibenzo [a, c] cyclohepten-5-one
(39) . ' ' Ketone 39. was obtained in 82% yield from a
small scale initial reaction with no effort to maximize the
23
Synthetic Scheme Cl Cl
NaOH
-7
1) 170°
2) CH^CN (aq.)
"^: — — 2"
Hj/Pd
CH3C02Et
-f-
LiCl
—7
DMF
TsNHNH,
TsNN
TsNHN
NaH
41
Figure 5
24
yield. The ratio of 37 *-° ^ depends on the extent of
reduction, the nature of the solvent, and the acidity of the
solvent. Factors which were not evaluated may also play a
role. Table 1 shows the ratio of 32 to 39. ^^^^n 1.1 equiva-
lents of hydrogen were introduced and the reduction was
carried out in a number of different solvents. Fortunately,
when ketone 39^ is formed as an undesirable side product, it
44
can be brominated and the broiriokctono 4_0 used in place of
chloroketone 37^ in the subsequent step.
Table 1
Solvent Effect on the Reduction of 6-Chloro-
5//-dibenzo [a,c] cyclohepten-5-one (36)
Solvent 37/39
Ethylacetate (1% HOAc) 5.2
Glacial Acetic Acid 3.0
Benzene/50% Cyclohexane 0.9
Ethanol 0.3
Both ketone 3_9 and cliloroketone 37^ have unusual niur
spectra which exhibit remarkable variation v/ith solvent. In
CDCI3 the spectrum of 3^ shows only aromatic protons and a
sharp singlet at t 7.00; in benzene-ds, the upfield singlet
becomes the expected AA'BB' multiplet. In benzene-de the
60 MHz nmr spectrum of chloroketone 37. shows aromatic protons,
a sharp triplet at t 4.62, and a sharp doublet at t 7.05
(J=7.5 Hz); in acetone-dg/ tlie spectrum is the textbook ABX
pattern (v= t 6.81, v = t 6.48, v = i 4.11, J =13.5 Hz,
J-v=9.0 Hz, J_,^=4.5 Hz); the 60 MHz spectrum in CCl^ has
AA DA
accidental coincidences that make the ABX pattern somewhat
less obvious (v = t 6.84, v = t 6.61, v = t 4.52, J =13.5 Hz,
Nmr Spectra of 39
25
? '^'^' V
I*
-I-
I Solvent: CDCl.
jtt "*,iri. . .tf.
*«w«^
Solvent: CgDg
Figure 6a
26
Nmr Spectra of 37
T I " I , I I I .' "J.
=^
CI
Jl
37
4:!i — 4k
i
Solvent: Acetone-d,
-- ^- . w T::rrrTwrTr-y"T v/^ .. ■■ ¥ -r -w . -T
5
J
4
Solvent: CCl,
!~
I
■ If -.--■y --.--y- .- ^ >am y , y , y _, y . y
_jil
•Ih — '(h
Solvent: CgDg'
>**^^ "y^^— - ij 1 — -- la r* ^<*'%
i
Figure 6b
27
J-„=12. Hz, J„^=3. Hz). Spectra in various solvents are
AX bA
shown in Figure 6a {6 ,7-dihydro-5//-dibenzo [a, c] cyclohepten-
5-one (_39) ) and Figure 6b (6-chloro-6 jV-dihydro-Sff-dibenzo-
tfljC] cyclohepten-5-one (37^)). These tv;o products of the same
reaction offer an amusing nmr study. It is particularly
notable that in spectra of the chloroketone 37^ coupling con-
stants as well as chemical shifts vary with solvent, pre-
sumably due to a different average molecular conformation in
each solvent. Since J, v=J„„ in benzene-dg , chloroketone 37
apparently assumes an average conformation in which the
H -H dihedral angle is identical to the H, -H dihedral angle
^ X ox
(i.e., H6 is, on the average, perfectly staggered between
the two H7 protons) in this solvent.
Dehydrohalogenation to the desired ketone 3£ is readily
accomplished under conditions similar to those employed by
45
Collington and Jones for the preparation of other tropones.
Spectral and physical properties of the final product (38)
are identical in all respects to the ketone 38* prepared in
37
a standard way. Conversion to the tosylhydrazone (4_1) and
formation of the tosylhydrazone sodium salt (41* ) were carried
out under conditions similar to those reported. The carbene
32 was generated from the salt by pyrolysis or by pyrex
filtered photolysis.
*
Authentic 5ff-dibenzo [aj e] cyclohepten-5-one (38^) was
prepared by Dr. P. Mullen.
28
Dibenzo [oj c] cycloheptatrienylidene 3_2 mimics the mono-
annelated cycloheptatrienylidene _3 in its facile rearrange-
1 2
ment when thermally generated in solution. ' In benzene
at 125 it rearranges cleanly and forms 9- (2 , 4 , 6-cyclohepta-
trien-1-yl) -phenanthrene (4^) quantitatively. Photolytic
42
generation at room temperature in benzene also produces the
phenanthrylcarbene addition product 4_2 as the major product
although the yield is less than quantitative. The rearrange-
ment seems to be rather sluggish when the aromatic carbene
32 is formed photolytically at -60° in 1:2 benzene-tetrahydro-
furan. Less than 0.2% yield of the phenanthrylcarbene addi-
tion product to benzene 4_2 is isolated. Other work with
phenanthrylcarbene 32 under these conditions indicates a
similar amount of tetrahydrofuran insertion products also
^ 46 ^
form. The nmr spectrum of the product mixture obtained
when dibenzo [a, c] cycloheptatrienylidene 32^ is photolytically
generated at -60 in tetrahydrofuran in the absence of any
other reactant indicates largely aromatic material with less
than 10% yield of compounds containing the phenanthrene
moiety. Yet, rearrangement is certainly occurring to a small
but significant degree (0.05 to 10%) even at these low tempera-
tures.
29
The aromatic carbene 32^ does not, however, react with
olefins prior to rearrangement as do other aromatic carbenes
1 2
such as 4 ,5-benzocycloheptatrienylidene ' _3 and cyclohepta-
47 48
trienylidene 2^. ' Even at temperatures so low that
products from the rearranged carbene 3_3 were isolated in only
very low yield, no evidence for the spiro-adducts to styrene
or dimethyl fumarate could be obtained. The products
observed from photolysis of 5ff-dibenzo [a^e] cyclohepten-5-one
tosylhydrazone sodium salt 41' in tetrahydrofuran at -60
with an olefinic trap present were similar to those obtained
in the absence of a trap. This is unexpected since carbenes
2 and 3 give spiro-adducts with dimethyl fumarate and styrene
47-49
under these conditions.
However, a reactive species can be trapped with dienes.
Photolysis of the sodium salt of 5fl-dibenzo [a, c] cyclohepten-
5-one tosylhydrazone 41 ' at -6 0 in the presence of cyclo-
pentadiene or furan with dry tetrahydrofuran as co-solvent
gives the Diels-Alder adduct of the cyclopropene intermediate
5£ with the diene, endo-2,3- (o-biphenylenyl) -tricyclo-
2 4
[3.2.1.0 ' ]oct-6-ene (43) or 1,7- (o-biphenylenyl) -endo-
2,5-epoxynorcar-3-ene (44) , respectively (73% and 47% yields)
43
44
30
43
44
As long as the photolysis is stopped shortly after all
the tosylhydrazone salt 41' has decomposed, adduct 4_3 is the
only isomer found to a limit of detection of about 1%. The
spectral properties leave little doubt that it is the endo
isomer. An ir band at 1045 cm indicative of a cyclopro-
pane ring is observed. The magnitude of the coupling
constant for the vicinal cyclopropane hydrogens, J- ^=2.8 Hz,
requires they be positioned ti'ans on a tricyclo [3 . 2 . 1 . 0^ ' '*] -
octane structure, ~ and the H4 chemical shift (x 9.39)
demands that this proton (H4) lie on the same side of the
cyclopropane ring as the aromatic substituent — this being,
of course, the only rational geometry (these features are
also apparent in the spectrum of the furan adduct 44). The
endo structure for 4_3 is also suggested by the magnitude of
the H4 cyclopropane hydrogen coupling to the adjacent
bridgehead proton, J^ ^=2.6 Hz, which is of the appropriate
magnitude only if the H4 proton is exo. Consistent with a
trans orientation of H3-H4 , H3 must be syn. This is cer-
tainly the case since were H3 anti , long range coupling to
^^anti ^°"1«^ ^e expected. ^° '^"^ The very sharp doublet
31
observed for HI (J_ ^=2.8 Hz, only) even in an expanded
100.1 MHz spectrum and the lack of any sharpening of this
signal v;hen either methylene bridge proton is irradiated
belies the possibility that H3 is anti . The vinyl protons
appear as a narrow multiplet approximating a triplet (60
MHz) in ?dduct 4_3, at t 3.95, significantly upfield from
2 4
vinyl protons observed in spectra of known tricyclo [3 . 2 . 1. 0 ' ]
oct-6-ene compounds with the cyclopropane ring exo , but
8sv^ oa
50
consistent with an endo structure. The high field position
of the cyclopropyl hydrogen H3 at t 7.4 9 requires that it be
syn on an endo ring. The best model for this compound is
2 4
enJc-2, 3, 4-triphenyltricyclo [3.2.1.0 ' ]oct-6-ene with the
55
3-phenyl anti. In its nmr spectrum the vinyl protons
appear at x 3.77 and the syn cyclopropane hydrogen at x 7.53,
in line with spectrum of adduct 43^. Finally, the similar
chemical shifts of the methylene bridge protons, H8 and
syn
H8 . , suggest that the cyclopropane ring is not in near
proximity to these protons .
Unassailable proof that the isomer formed (4_3) has the
endo-anti configuration is essential to the contention that
this compound results from a Diels-Alder reaction of the
32
cyclopropene intermediate 5c with cyclopentadicne. There is
no example of the formation of any stereoisomer other than
the endo-anti isomer in cycloaddition reactions of 3-mono-
substituted cyclopropenes with cyclopentadicne. -''-'0»^^'^"
Spectral evidence is equally convincing in support of
an enJo-epoxy structure for 44^, the major product formed on
reaction with furan. However, this reaction is not as clean
as that with cyclopentadiene. A number of unidentified minor
products (including at least three products from subsequent
photolysis of AA) are always obtained along with 44. A small
amount of the exo-epoxy isomer, which would presumably be
57
the less stable isomer, may have escaped detection, although
currently there is no evidence for its formation. There are
a number of previous reports of cyclopropenes reacting with
furans to yield only the exo adduct. ~ The structure
assignment rests on the absence of coupling of the cyclo-
propyl proton H6 with the adjacent bridgehead proton, H5, as
expected if H6 is endo on the oxy-norbornene portion of the
57 58
molecule, ' and on the abnormally low field position
(t 6.39) of the cyclopropyl proton H7 which suggests its
proximity to the bridging oxygen ' (cf., the analogous
33
proton at x 7.49 in 43) . The molecule 4_4 is also particularly-
well suited for structure determination by an analysis of
lanthanide-induced proton nmr shifts. The result of addi-
tion of a small amount of Eu(fod)3 to an nmr solution con-
taining adduct 4_4 is shown in Figure 7. A dramatic down
field shift of the cyclopropyl hydrogen H7 of even greater
magnitude than that experienced by the alkoxy protons at the
bridgehead positions occurs. (All these protons are situated
at a similar angle to the Eu-0 contact line.) A rough calcu-
lation of the agreement factor for the exo-epoxy isomer
(R=0.36) and for the endo-epoxy isomer (R=0.05) provides
convincing evidence that the molecular geometry is that
claimed (the lanthanide atom was assumed to be directly
above the oxygen in the plane bisecting the bridge at a
o
distance of 3. A; distances and angles were measured manually
from a Dreiding Model. Only nonaromatic protons were used
in the computation and only shift data from the spectrum at
maximum mole ratio Eu(fod) 3 :4_4_) .
• • Although good yields of adducts £3 and 44^ are obtained
at low temperatures, and volatile and reactive dienes are
most conveniently employed below room temperature, the for-
mation of these adducts is possible at any temperature at
which the aromatic carbene 2_2. undergoes rearrangement.
Photolysis of the tosylhydrazone salt 41' at room tempera-
ture in neat furan produces 43% yield of the adduct 44 .
Yields from the low temperature and the room temperature
photolysis experiments are quite comparable considering the
scale on which these reactions are run. Also, pyrolysis at
34
*Jmr Spoctra of 4_4 with Increasing Amounts of Eu(fod)3 Present.
»» mum I III i«^
44
tWIK^fj^^llfifltl^l^l^O
tlMMMilMMiMMUlM
Figure 7
35
115° gives 11% of this furan adduct 44^. In each case the
encfo-epoxy isomer of 44_ is formed with no indication that
any exo-epoxy isomer is generated. Unfortunately, adduct
44 is thermally unstable at the temperature necessary for
thermal formation of carbene 3_2. 43^ is also photolytically
unstable. The primary result of thermolysis (and a minor
product from photolysis) of adducts such as 4_3 and 4_4
appears to be structures formed by cleavage of the most
strained cyclopropane ring bond (for example, 10 , 13-methano-
9Z/-cyclohepta [Z] phenanthrene and 10 ,13-epoxy-97i-cyclohepta-
[Z]phenanthrene) . Excessive photolysis of £4_ produces three
4£'
products and an intractable residue. The m.ajor product seems
to be a phenanthrene fused alcohol (possibly 4_4 ' ) in 40-60%
yield along with two minor products (10-15% yield) , one of
which is similar to the major pyrolysis product. However,
these are only tentative structure assignments based solely
on nmr spectra. Such secondary thermal and photolytic
products offer little relevant information pertaining to the
question at hand. Though perhaps it should be mentioned
that thermal generation of phenanthrylcarbene 3_3 from the
aldehyde tosylhydrazone sodium salt A5' gives different
major products. This suggests efficient trapping of the
36
cyclopropene 5£ in high as well as low temperature rearrange-
ments, but with extensive thermolysis of the initially formed
adduct (presumably £4) at high temperatures. Since some of
the adduct 4_4 can be isolated from thermal as well as
photolytic generation of the carbene SJ.* this product clearly
cannot be the result of a secondary photo process.
Trapping of the cyclopropene intermediate 5£ under high
temperature conditions is best accomplished employing
2,3 ,4 , 5-tetraphenylcyclopentadienone (tetracyclone) in a
reaction modeled after that developed by Mitsuhashi in
st:udies with cycloheptatrienylidene 2_. Excess tetracyclone
must be destroyed by a cycloaddition with propiolic acid
followed by removal of acidic components, since the products
and tetracyclone cannot be separated directly by column
chrom.atography or preparative layer chromatography. 10,11,12,13-
Tctraphenyl-9//-cyclohepta [I] phenanthrene {46) is the major
product in about 50% yield contaminated with a trace of
9 ,10 ,ll,12-tetraphenyl-ll//-cyclohepta [Z] phenanthrene (4_7) or
possibly 9,10,11, 12-tetraphenyl-9tf-cyclohepta [I] phenanthrene
(47^'). The proposed structure of the minor impurity is sug-
gested by the nmr spectrum (t 4.52 for the methine proton)
which is as expected for a compound with a structure analo-
gous to the major product 10^ which forms on reaction of cyclo-
heptatrienylidene 2 with tetracyclone (x 4.63 for the methine
proton ) . A clear differentiation between the two possible
isomers 4J7 and £7' is not possible, although additional work
permitted an unambiguous assignment in the cycloheptatrienyli-
37
case. The principal product 10 , 11 , 12 ,13-tetraphenyl-9ff-
cyclohepta [Z-]phenanthrene (46^) is apparently the most stable
hydrogen shift isomer and is formed by acid catalyzed, base
catalyzed or thermal isomerization of less stable isomers.
The structure of this compound is clear from its spectral
properties. The uv spectrum shows the very weak longest
wavelength absorption so characteristic of phenanthrene at
X 357 nm with shorter wavelength bands obscured by the
max
tail of a more intense absorption due to another chromophore
in the molecule. The nmr spectrum shows the underside pro-
tons on phenanthrene at t 1.25-1.6 (m, 2H) just as expected
(phenanthrene itself also has these protons at x 1.25-1.6
6 2
(m, 2H) ) . The coupling constant J=12.5 Hz is consistent
with that generally observed for geminal coupling in confor-
6 3
mationally restricted cycloheptatrienes , azepines, and
diazepines. It is inconsistent with J, ^ which is generally
6.0-7.5 Hz and any long range coupling. Table 2 compares
the H-nmr spectral properties of 10,ll,12,13-tetraphenyl-9ff-
cyclohepta [Z] phenanthrene (4_6) with appropriate model com-
pounds .
6 3
9-Methoxy-6 ,7 ,8-triphenyl-5fi-benzocycloheptene is a
particularly good model for the product obtained in this
reaction. It, also, is apparently the most stable isomer
and is prepared from 5-methoxy-6 ,7 , 8-triphenyl-5ff-benzocyclo-
heptene by thermal isomerization. Heating either isomer in
refluxing xylene results in a mixture of the two isomers.
Likewise, heating 10 , 11 ,12 , 13-tetraphenyl-9ff-cyclohepta [I] -
38
Table 2
Nmr Spectral Properties of 4j6 and Similar Compounds
Compound
II (t) H (t) J T Reference
eg ax gem c
this
5.38 6.08 12.5 Hz >150° work
Cells 6.27 6.50 12 Hz 65 63
CeHs
7.1 8.5 11 Hz -143'
64 &
65
H. / H
7.10 (d, J, _= 7.0 Hz)
66
6.24 (d, J^ = 6.2 Hz)
17
39
phenanthrene 4^ in refluxing xylene produces some of the
isomeric compound (47_ or 41_' ) with an nrar signal at t 4.52
along with a good deal of material (s) with totally aromatic
protons. Preparative layer chromatography or recrystalliza-
tion (chloroform) fails to give a pure material..
Heating 10 ,11 , 12, 13-tetraphenyl-9tf-cyclohepta [I] phenan-
threne 46_ in an nmr spectrometer (tetrachloroethylene as
solvent) results in a distinct loss in spectral resolution
at about 150+10 . However, an average spectrum is never
observed at higher temperatures. On cooling to room tempera-
ture, a mixture of compounds similar to those that result on
refluxing in xylene is observed. The model compound 9-methoxy-
6 ,7 , 8-triphenyl-5ff-benzocycloheptene also has a high nmr
coalescence temperature (65 ) for the ring flipping process
that averages the axial and equitorial proton signals.
9ff-Cyclohepta [^] phenanthrene £6 would be expected to have
a substantially higher nmr coalescence temperature, and it is
not surprising that a temperature in excess of 150 is
required. However, with £6 the nmr coalescence temperature
is not necessarily due to conformational isomerization, but
may rather be a result of rapid hydrogen shifts or some
other process.
- The intermediate (presumably the cyclopropene 5c) which
reacts with dienes to produce these adducts has a sufficient
lifetime to be detected even after photolysis, and hence
generation of the initial intermediate 32^ has ceased. The
halflife of the reacting species 5£ is of the order of a few
minutes at -60 as determined by very crude late addition
40
experiments using cyclopentadiene. After photolyzing 41'
seven minutes at -60 , the light was extinguished and cyclo-
pentadiene (at -78 ) was added immediately to give a 4.7%
yield of adduct 4_3; a similar photolysis with addition of
the diene two minutes after photolysis ceased gave a 3.6%
yield of 4_3. It is unlikely that steady-state conditions
were achieved or that temperature, light intensity, and
other reaction variables were sufficiently similar to allow
more than a rough estimate of the half life (ca. 6 minutes
if first order; ca. 7 minutes if second order) . A rough
minimum activation energy for formation of the arylcarbene
33 from cyclopropene 5c^ would therefore be at least 11 kcal/
mole (an approximate frequency factor is taken from a similar
6 7
cyclopropene fission ) . The activation energy is probably
somewhat greater since it is doubtful that 5c^ entirely
decomposes via the arylcarbene 33 .
4 ,5-Ben20cycloheptatrienylidene 3^ is the premier
example of an aromatic carbene that rearranges to an aryl-
1 2
carbene m solution and has been extensively studied. '
At low temperatures in the presence of olefins spiro-
compounds result from trapping of the aromatic carbene _3.
1 2
Although the yield is poor, cyclohexene, ' dimethyl fumarate,
styrene, and substituted styrenes successfully react with
49
this aromatic carbene. As the temperature is raised, the
yield of products resulting from the rearranged carbene,
3-naphthylcarbene (4), improves.
41
If a cyclopropene intermediate is required for rearrange-
ment, it should also be possible to trap such an intermediate
from this carbene {3). When 4 ,5-benzocycloheptatrienylidene
(3) was formed in the presence of the diene, 1 , 3-cyclopenta-
diene, by low temperature photolysis, a small amount (16%
2 7 2 8
yield) of endo-5 ,6-benzotetracyclo [7 . 2. 1 . 0 ' .0 ' ]dodeca-
3,5,10-triene (48_) resulted. This is just the product
expected from reaction of the cyclopropene intermediate 5b
with cyclopentadiene in a Diels-Alder reaction. The molecular
geometry of this adduct follows from a comparison of its
spectra with those of the adduct 43- obtained from dibenzo-
[a,c]cycloheptatrienylidene (32^) and cyclopentadiene. Table
3 (on the following page) compares nmr spectra of 4_3 and 48 .
A structure argument similar to that presented for adduct
43 based on nmr spectral data can also be developed for this
adduct.
Reaction of 4 ,5-benzocycloheptatrienylidene {3) with
1,3-butadiene at low temperatures produces a number of
isomeric hydrocarbons. The major product is 4 , 5-benzotri-
cyclo [5.4.0.0 ' ] undeca-2 , 4 , 9-triene (49^), and a minor
<-^^
CO^
50
Table 3
Nmr Spectra (x)
H
H.
H,
Hj H.
7.49 9.39
6.61
6.89
3.95 7.73
8.10
J ,=2.8 liz, J, =2.6 hz, J ,=6.8 Hz
diD tJC 66
7.52
9.65
6.93
7.05
4.1
7.9
8.18
J .=2.8 Hz, J, =2.6 Hz, J ,= 6.8 Hz
ab 'be ' ee
48
Table 4
K / ^68
H-nmr (x)
Compound
H
H.
H
9.45- 7.64(d) 7.47
9.75(m) J h=4.7 Hz
H, H
4.35- 3.84
4.55
H
Me0 2C
H
H.
H
7.6 4.5
CO2H
9.15 6.90
J ,=4.1 Hz
a,b
3.62
J ,=10.1 Hz
e,e'
43
product is the spiro-compound expected from addition of the
aromatic carbene to one double bond of the diene, 1-vinyl-
6,7-benzospiro [2.6]nona-4 ,6,8-triene (5£) . The spectral
and physical properties of the adduct 49_ are just as antici-
pated for a benzonorcaradiene incorporated into a 3-norcarene.
Table 4 (on the preceding page) lists the nmr spectral
features. The nmr spectrum has cyclopropane protons with
chemical shifts and coupling constants just as observed in
the nmr spectra of other similar adducts (cf., spectra of
43, 44 , 48 , and 49_ in Figure 8). Also, the spectral proper-
ties of the spiro-isomer 5_0 are consistent with those of
12 49
other similar 6 ,7-benzospiro [2. 6]nona-4 ,6 ,8-trienes. ' '
In fact, there are amazing similarities between the ir
spectrum of 5£ and that of l-phenyl-6 ,7-ben20spiro [2. 6] nona-
4 9
4,6,8-triene (as well as other analogous phenyl substituted
compounds) . Nmr spectra of spiro-products obtained on addi-
47 48
tion of cycloheptatrienylidene (2^) to olefins ' also
agree v;ell with the spectrum of 5£. Pertinent nmr spectral
features along with similar features in model compounds are
collected in Table 5.
With l-vinyl-6 ,7-benzospiro [2. 6] nona-4 ,6 ,8-triene (50)
in hand, it is possible to offer evidence against one possible
objection to a cyclopropene trapping mechanism for formation
of the major isomer 4_9. Cycloheptatrienylidene (2^) has been
shown to react with the diene, cis-1 , 3-pentadiene , to yield
1-propenylspiro [2.6] nona-4 ,6,8-triene which rearranges
44
"H-nmr Spectra of Adducts
; .i y i
F
w*
u
! .<
uU'''lj
)
•t^tf^itttm
J
u
Wu..Uui
48
Figure 8
45
Table 5
Nmr Spectral Properties of 5_0 and Similar Compounds
Compound
H^(t) n^ (t) H^ (t) H^{t) H^(t)
a 8.25-9,2 4.2-4.8 4. 75-5. 2 3.72 4.75-5.2
3.84
J, =11.5 Hz
de
H'_ CeHs
8.45-8.8 3.73 4.82
3.84 5.31
a " " J^g-11.5 Hz
8.55-9.05 4.5-5.3 3.5-4.2
and 9.40
48
thermally to 8-methylbicyclo [5 . 4 . 0] undeca-1 , 3 , 5 , 9-tetraene
(Figure 9a) . A similar mechanism with cycloheptatriene to
norcaradiene isomerization can be ruled out as a possible
mode of formation of 4^ since l-vinyl-6 ,7-benzospiro [2. 6] nona-
4,6,8-triene (50^) is thermally stable to molecular distilla-
tion at 70 . It also fails to undergo conversion to 4_9 when
subjected to the photolysis and workup conditions under which
adduct 4_9 is obtained (to a limit of detection of better
than 1%, ca. 75% of starting material being recovered).
Thus the adduct 4_9^ cannot be formed from 50^ by a secondary
reaction (Figure 9b) of either a thermal or photochemical
nature.
46
A Tv.'o-stC'p Mechanism for Adduct Formation
a)
+
CH
CH
b)
' +
^
^
V
Figure 9
47
The lower adduct yield that results v;hen 4 , 5-benzocyclo-
heptatrienylidene {3) reacts with cyclopentadiene than when
dibenzo [a,c] cycloheptatrienylideno (^2) reacts v/ith this
diene (i.e., 16% yield from 3_, 73% yield from BJ.) provides
some assurance that an intermediate in v;hich the annelated
rings experience a decrease in resonance energy is not the
reactive species. Thus it seems unlikely that a strained
allene 51^ or a zwitter ionic species (for example 52^ or 6c)
reacts with the diene. However, other more convincing
arguments against some of these species have been offered
previously. ■'■'^'■^'^'^^ Unfortunately, the low yields from 3_
T. -H
51 52 6 .
may be in no way related to the efficiency of cyclopropene
trapping. A red- orange amorphous solid forms on photolysis
of 4,5-benzotropone tosylhydrazone salt (S^' ) and may possibly
prevent complete photolysis of the salt by its more efficient
light absorption. Typically, low yields result from photo-
lytic generation of 4 , 5-benzocycloheptatrienylidene {3)
regardless of the mode of reaction (i.e., trapping of the
cyclopropene, trapping of the aromatic carbene, or trapping
of the arylcarbene after rearrangement) . Also, the requisite
longer photolysis time may result in more extensive photo-
rearrangement of initially formed adducts.
48
However, thermal generation of 4 ,5-benzocyclohepta-
trienylideno (_3) (and hence the cyclopropene 5b) in the
presence of tetracyclone clearly implies less efficient
cyclopropene trapping than occurs in the analogous reaction
of dibenzo [a,c] cycloheptatrienylidene 32_ (and hence the
cyclopropene 5£) with tetracyclone. Thermolysis (115 for
2 hours) of 4 , 5-benzotropone tosylhydrazone salt (53^') in
tetrahydrofuran containing tetracyclone yields a single
C39H28 hydrocarbon product, 7 , 8 , 9 , lO-tetraphenyl-Q/Z-cyclo-
hepta (a) naphthalene (54^) in 9% yield. The spectral proper-
ties of this product are as one would predict based on those
of major hydrocarbene products resulting from reaction of
other aromatic carbenes (i.e., 2_ and 3_2) with tetracyclone
(for example, the nmr chemical shift of the methine proton
is as anticipated — see Table 6) .
The major products from this reaction are apparently
3-naphthylcarbene tetracyclone addition products, g-naphthyl-
tetraphenylphenol (5_5) and 6a, lla-dihydro-7 , 8 , 9 , 10-tetra-
phenylbenzo [a] naphtho [2 ,3-J] furan (56_) . An analogous phenol
is formed on addition of diazomethane to tetracyclone.
The spectral and chemical properties suggest that 55^ is a
polyarylphenol [ir: 3530 cm" , OH; nmr (CDCI3) t 4.78 (s,
removed by shaking with D2O) ; orange coloration in the
presence of NaOH] . It has a molecular weight of 524 (mass
spectrum) and the correct elemental analysis for a CuoHaeO
species. Only a tentative structure assignment is possible
for 5_6. Spectral properties are consistent with the structure
assigned, and the compound is certainly a CucHasO compound
49
Table 6
Hydrocarbons from Reactions with Tetracyclone
^H-nmr (t) Yield of
(methine proton) Adduct
Compound
CeHs
CeHs
>
■-4--IL.
r\
4 ""
^CsHs
4.63
25%
10
CeHs H
4.57
9%
54
CgHs H
4.52
50%*
♦The isolated material is mainly an H-shift isomer with a
trace of this material as an impurity.
50
(1:1, 3 : tetracyclone) , since the parent ion in the mass
spectrum is found at m/e 524.
A lower yield of the typical cyclopropene adduct is
expected if cyclopropene 5b is less stable (and hence is
available in the reaction mixture for a shorter period of
time) than cyclopropene intermediate 5£. Although other
explanations for these results are possible, the hydrocarbon
yields are completely consistent with the original expecta-
tion based on simple Huckel molecular orbital predictions
that 5b would be less stable than 5£. Similar reasoning
rules out product formation from the less stable allene of
32. It is at least clear that none of the three compounds
isolated (54_, 55^, or 56^) is a precursor of any other.
Neither thermolysis nor acid treatment converts any one product
to any other.
Cycloheptatrienylidene (2^) does not undergo rearrange-
ment in solution so trapping of a rearrangement intermediate
would not be expected. However, 2_ does react with dienes
to give products with the general structural features antici-
pated if they result from the cyclopropene intermediate 5a^
undergoing cycloaddition with the respective diene '
(i.e., cycloheptatriene rather than norcaradiene isomers of
adducts similar to 4_3, 44_, 4_8, and 4^) . In other work
(Chapter I) the reaction of cycloheptatrienylidene (£) with
tetracyclone has been shown to be consistent with cyclopro-
pene trapping but not necessarily requiring product forma-
tion by this mechanism.
51
In one instance, reaction of the carbene 2_ with cis-
1,3-pentadiene, the adduct has been convincingly shown to
not bo the result of a Diels-Alder reaction of a cyclopro-
pene intermediate (5a^) , but rather to be the final product
of a two-step process as shown in Figure 9a (page 46) .
Since cia-l, 3-pentadiene is an extraordinarily poor diene
for a Diels-Alder trapping reaction, its reaction may not be
representative of those of other dienes which react to give
products consistent with trapping of the cyclopropene 5a_
and with no indication of isomeric adducts that rearrange
to the observed product.
The possibility that the aromatic carbene 2_ is in rapid
equilibrium with the cyclopropene intermediate 5a in spite
of the lack of further rearrangement to 1^, seems worthy of
experimental test. A clear differentiation is not possible
employing most diene traps since (as outlined above) both
the aromatic carbene 2^ and the cyclopropene 5a react to
eventually produce the same product. However, when cyclo-
heptatrionylidene (2^) is generated thermally in the presence
of furan, the structure of the resultant adduct 57^ suggests
that cyclopropene trapping is not the mechanism of its for-
mation. The isomer obtained is exo-1, 4-epoxy-4a^-benzocyclo-
heptene (_57) . The spectral properties are as expected from
those of the other diene adducts. Lanthanide-induced proton
nmr shifts leave little doubt that the exo-epoxy isomer is
obtained. Spectra with increasing amounts of shift reagent
present are shown in Figure 10. H4a is clearly situated
52
■'"ll-ninr Spectra of 52 with Increasing Amounts of Eu(fod)3 Present
57
Jl
I
\J'
I
J^JJoiw
^t«W¥«WlMN«*4ti^
Figure 10
53
closer to the oxygen tlian the vinyl protons H2 and H3 by
virtue of the greater induced nmr shift it undergoes on
addition of Eu(fod)3 (all angles being identical to ±1 ).
A rough calculation (with the sarie assumptions as employed
for the previous treatment of adduct 4_4_) of agreement factors
(exo: R=0.06; endo : R=0.16) confirms the exo geometry and
amounts to a structure proof. Formation of this isomer, 57 ,
by cycloaddition of the cyclopropene 5a to furan requires an
endo- transition state. Since an exo- transition state is
necessary in the reaction of dibenzo [cj e] cycloheptatrienyli-
dene (3 2) (via the cyclopropene 5c) with furan to produce the
observed adduct 4£, and since there is strong evidence for a
cyclopropene 's participation in this reaction, it is unlikely
that 57^ results from cycloaddition of the cyclopropene 5a,
and a two-step process is indicated. This is especially
true since there seems to be no obvious alternative explana-
tion for a reversal in mode of cycloaddition. Steric dif-
ference in 5a_ and 5c appear minor, and secondary orbital
35 7 0
interactions ' are similar (in fact, if favorable inter-
action between the oxygen orbitals of furan and the conju-
gated TT-system of the cyclopropene accounts for exo-cyclo-
addition, 5a is more likely to react exo than 5£) . Hov/ever,
since factors affecting the mode of furan cycloaddition are
poorly understood, this experiment fails to offer more than
tentative implication of a two-step reaction.
54
Due to the relatively small loss in resonance energy
(Figure 4) accompanying isomerization , phenanthrylcarbene
(33) might be capable of rearrangement to the cyclopropene
intermediate 5£ followed by cycloaddition with dienes. This
intermediate 5c might well be generated oven if further
reorganization to the aromatic carbene 32^ v;ere not thermo-
dynamically feasible. However, generation of 3_3 in the
presence of furan fails to produce any trace of adduct 44_
under either thermal (115 ) or photolytic {-GO ) conditions
(limit of detection: 0.1%). Thus, an encx'getic ordering
of the intermediates is precluded since one cannot ascertain
whether thermodynamic or kinetic factors prevent detection
of the cyclopropene intermediate 5c.
Cyclopropenes occasionally react with amines to produce
71
cyclopropylamines , but generally these reactions are
sluggish, requiring a substantially polarized or highly
15
electron deficient double bond. The cyclopropene inter-
mediate 5£ would hardly be expected to undergo nucleophilic
addition of amines. However, an intermediate such as 6c
(or another dipolar species) should be quite susceptible to
amine trapping. In view of the other evidence presented
here, it is not surprising that no indication of addition
was obtained when dibenzo [a^ c?] cycloheptatrienylidene 32 was
generated in the presence of diethylamine. The product mix-
ture was similar to that produced in the absence of trapping
reagents or in the presence of ineffective traps.
55
Nucleophilic addition of amines is the strongest
evidence implicating a 2fl-azirine intermediate 59^ in the
rearrangement of phenylnitrene 5£ to 2-azacycloheptatrienyli-
72
dene £0. The reaction of amines with azirines is expected
to occur more readily than analogous reactions of amines
:N:
58
with cyclopropenes due to the greater polarity of the double
bond, and amine addition to 2ff-azirines has been experi-
73
mentally demonstrated. The extreme specificity for amines
of the reactive intermediate resulting from phenylnitrene 58^
is truly remarkable, particularly, since the presumably
similar cyclopropene intermediate 5c_ is totally unreactive.
Sundberg and coworkers have shown that 2-diethylamino-3^-
azepine (61a, R,R'=Et) is best prepared with the amine
74
present as a very dilute solution (about 2% in THF) . This
report was confirmed on a preparative scale. In fact, a good
yield of azepine 61b (R=r.-butyl, R'=H) results from reaction
of phenylnitrene (from photolysis of phenyl azide) with an
equimolar amount of the amine. This is particularly remark-
able since phenyl azide should be an equally effective trap
75
for the preposed 2//-azirine intermediate 59.
56
Furan also fails to react with the intermediate from
phenylnitrene. This, too, is unexpected since 2//-azirines
generally undergo 2+4 cycloadditicn reactions with dienes
only slightly less readily than do cyclopropenes . For
example, the conditions for reaction of tetracyclone with
3-methyl-2-phenyl-l-azirine (3:4 inolar ratio, refluxing
"7 f
toluene, 6 days, C5% yield ) are just slightly more vigor-
ous than those for reaction of tetracyclone with 1,2,3-
triphenylcyclopropene (1:1 inolar ratio, refluxing benzene,
77
2 days, 75% yield ). Yet, with an equimolar quantity of
amine as trap, the yield of 3//-azepine 61b is identical
when furan is substituted for tetrahydrof uran as the reaction
solvent. As mentioned previously, there is also no evidence
that phenyl azide cycloaddition with the intermediate occurs,
and a highly strained azirine such as 59^ should be particu-
7 5
larly susceptible to cycloaddition vv^ith phenyl azide. In
all, the evidence for azirine 5_9 as an intermediate in phenyl-
nitrene rearrangements is decidely weak. The Wolff inter-
mediate £2 seems equally satisfactory. However, attempted
trapping experiments with dienes which are more susceptible
to rapid reaction with 2//-azirines would be of interest.
62
57
An argument based on relative ir-bond order of the
reacting bond led to the correct choice of a cyclopropene
mechanism for carbene-carbene rearrangements and a similar
analysis when applied to the reorganization of heterocyclic
carbenes ' and nitrenes strongly suggests a Wolff
mechanism for these rearrangements (via an intermediate or
transition state similar to £ or 62_) . An evaluation of sub-
stituent effects on the direction of nitrene rearrangement
from studies of arylnitrenes (particularly ort^zo-substituted
7 8
phenylnitrenes ) suggests that nitrene reorganizations
occur by a VJolff mechanism since the least stable 2//-azirine
is often required to produce the observed product. However,
such an analysis is not without question, and in fact the
bond of highest ir-bond order does migrate in arylnitrene
rearrangements just as it does in carbene rearrangements,
suggesting a 2Z?-azirine intermediate. The results reported
here offer little evidence that would permit a mechanistic
distinction. Clearly other factors which may influence the
4
rearrangement require evaluation (intermediate energetics,
singlet- triplet crossing, prior azide-trap association, and
possible simultaneous nitrogen loss with reorganization
7 8 7 9
influenced by azide conformation, ' for example) . Naphthyl
8 0
azide may fail to rearrange since a Wolff mechanism leads
to the very high energy intermediate, 3 , 4-benzoazacyclohepta-
trienylidene (analogous to 8) , or it may fail to rearrange
for reasons similar to those that prevent the rearrangement
of naphthylcarbene (A) via a cyclopropene intermediate 5b
5B
(yet, phenylnitreno 5jB rearranges in solution, although
phenylcarbene 1 does not. ) . While a cyclopropene 5^ is
clearly implicated in rearrangement of carbenes into and out
of carbocyclic systems, the older and better studied aryl-
nitrene rearrangement Litill requires mechanistic evaluation.
CONCLUSION
A concerted rearrangement via a cyclopropene-like transi-
tion state is unainbiguously ruled out as a mechanistic pos-
sibility for carbene-carbene rearrangements occuring in solu-
tion. The evidence presented leaves little doubt that fused
cyclopropene intermediates are generated from dibenzo [a, .] -
cycloheptatrienylidene (32) and 4 ,5-benzocycloheptatrienyli-
dene (3) . That the cyclopropenes 5b and 5c are thus inter-
mediates along the rearrangement pathway is implied.
However, other alternatives must also be considered.
It is clear that irreversible cyclopropene formation and
irreversible rearrangement cannot be competitive modes of
destruction available to these aromatic carbenes. When
forced by thermolysis at 120±10°, dibenzo [a, .] cyclohepta-
trienylidene (32) rearranges and is trapped in 95% yield as
the benzene addition product 42 of phenanthylcarbene. This
permits no more than 5% irreversible formation of cyclopro-
pane 5c. However, under similar (120110°) thermolysis condi-
tions, the Diels-Alder adduct 46 of cyclopropene 5c and
tetracyclone is isolated in 50% yield. Consequently, the
suggestion that competitive, irreversible cyclopropene for-
mation occurs and does not lead to the arylcarbene is refuted.
Evidence based on a previous study of 6-naphthylcarbene (4)
59
60
formation from 4 , 5-benzocycloheptatrienylidene (3_) » along
with the tetracyclone trapping reported here leads to a
similar conclusion in the case of carbene 3^.
A more serious difficulty is the possibility that the
aromatic carbenes 3^ and 32^ are in rapid equilibrium with the
cyclopropenes 5b and 5£, respectively, v/ith rearrangement
occuring from the aromatic carbenes rather than the cyclo-
propenes. This is essentially the same problem that pre-
5b
vented a determination of whether the 7//-benzocycloheptenes
£ and 10^ isolated from cycloheptatrienylidene 2^ addition to
tetracyclone resulted from reaction of the aromatic carbene
2 or the fused cyclopropene 5a^ (Chapter I) . When there are
a number of r idly equilibrating intermediates, it is often
difficult to otate with certainty which intermediate produces
the observed product. In general, unless structures of the
final products provide convincing evidence, it is seldom pos-
sible to deduce from what point equilibrating intermediates
convert to products.
61
The photochemical Wolff Rearrangement is a pertinent
example. Although an oxirene intermediate (or transition
state) is forir-.ed, it does not produce the rearranged
8 1
products. Oxirenes in carbonylcarbene rearrangements may
offer a very close analogy to cyclopropenes in aromatic
carbene rearrangements. Both may be side species not involved
in the rearrangement.
However, some reasons for rejecting this possibility can
be offered. In the first place, conclusive evidence that
cyclopropene trapping occurs has only been obtained in the
case of those carbenes (i.e., ^ ^^^ ID that rearrange in
solution. Evidence for cyclopropene trapping from cyclo-
heptatrienylidene 2^ (which does not rearrange in solution)
is lacking. Secondly, all arylcarbenes and aromatic carbenes
that have been observed to rearrange either in solution or in
the gas phase, rearrange predominantly, if not exclusively,
via the more stable of the two possible cyclopropene inter-
mediates (if two different intermediates are possible) . Thus
the direction of rearrangement can be predicted from stabili-
ties of the intermediate cyclopropenes. This, in substance,
is equivalent to the statement that addition to the bond of
highest ir-bond order occurs. Finally, the minimum conditions
necessary for carbene-carbene rearrangements are determined
by structural feature associated with the cyclopropene, insofar
as the stability of the cyclopropene reflects the stability
of the transition state for the rearrangements. 1-Acenaphthyl-
carbene (17) fails to rearrange in solution (due, presumably.
62
to the highly strained cyclopropene intermediate 5d neces-
sary) v;hile mrithano-lOTi-annulenylcarbene £3 (having a less
strained cyclopropene intermediate 5e^) rearranges readily.
solution
160° '
17
5d
solution
160°
63
5e
Similarly, 4 , 5-benzocycloheptatrienylidene 3^ rearranges
rapidly in solution (due, presumably, to the lesser loss in
resonance energy associated with formation of the cyclopro-
pene intermediate 5b) while cycloheptatrienylidene 2 fails
to rearrange in solution (since it loses much more resonance
energy on formation of 5a) . Therefore rearrangement via a
S J
2
solution
125°
solution
125°
5a
cyclopropene intermediate 5^ seems likely, if not certain, and
may be accepted in the absence of evidence to the contrary.
It may well bo the case that the aromatic carbene, the
cyclopropene, and the arylcarbene form successively and
irreversibly. It has been experimentally demonstrated that
arylcarbene 3_3 does not reversibly form the cyclopropene 5c.
An alternative synthesis of the cyclopropene (best, 5b) and a
63
search for spiro-adducts due to the aromatic carbene (_3) are
required as an empirical test of equilibration of 3 and 5b.
If the aromatic carbene is not formed from the cyclopropane
precursor, the mechanistic sequence of intermediates in
carbene-carbene rearrangements would be unequivocally
established. However, this experiment remains to be carried
out, and its results are not readily predictable, even if the
mechanistic sequence for rearrangement is as proposed. In
the gas phase, the reversibility of this rearrangement has
been previously demonstrated. '
Since cyclopropene trapping is very characteristic of
carbenes that rearrange in solution, it offers a method of
establishing if observed rearrangements are actually carbene-
carbene rearrangements. For example, attempted cyclopropene
trapping might allow proof of the mechanism of product forma-
tion on treatment of f errocenyltropylium fluoroborate with
base which has been suggested to involve a carbene-carbene
8 2
rearrangement. Similarly, cyclopropene intermediate 5e
(t-Pr) pNEt
BFt
Products
in the methano-lOiT-annulenylcarbene rearrangement might
be sought.
Initial efforts along this line, experimental tests
to detect a 2//-a2irine intermediate 59 in arylnitrene
64
rearrangoments, proved futile. This suggests that an alter-
native mechanism pertains in this rearrangement. However,
this one piece of negative evidence is insufficient to allow
any definite conclusion. Yet the mechanism of arylnitrene
3 4 7
rearrangements should not be assumed {as they often have ' ' )
to l:»e analogous to the carbon analogue. The intermediacy of
TO "7y( TO O^
an of tpostulated ' ' ' 2//-azirine intermediate 59^ in
the rearrangement remains open to question. Generation of
phenylnitrene in the presence of more reactive dienes will
be ol interest.
EXPERIMENTAL
General. — Melting points were taken in a Thomas-Hoover
Unimelt apparatus and are uncorrected. Elemental analyses
were performed by Atlantic Microlab, Inc., Atlanta, Georgia.
Accurate mass measurements were provided by the High Resolu-
tion Mass Spectrometry Laboratory, Florida State University,
Tallahassee, Florida. Ultraviolet and visible spectra were
recorded on a Gary 15 double-beam spectrophotometer using
1-cm silica cells. Infrared spectra were recorded with a
Beckman IR-10 spectrophotometer. In all cases where the
KBr pellet technique was not used, sodium chloride plates
were substituted. Nuclear magnetic resonance spectra were
determined on a Varian A-60A high resolution spectrometer.
A Varian XL-100 spectrometer was used for double resonance
experiments and for some studies with Lanthanide shift
reagents. Chemical shifts are reported in tau (t) values
from internal tetramethylsilane standard. Low resolution
mass spectra were determined on a Hitachi model RMU-6E mass
spectrometer .
Analytical thin-layer chromatography (tic) was accomp-
lished on 2 in. x 8 in. plates coated in these laboratories
with 0.25 mm layers of E. Merck HF-254 silica gel; prepara-
tive work was conducted on 8 in. x 8 in. plates coated with
1.0 mm layers of HP-254 silica gel. Components were
65
66
visualized by their quenching of fluorescence under uv light.
Analytical gas-liquid chromatography was accomplished with a
Varian Aerograph Series 1200 flame ionization instrument
using a 10' x 1/8" or a 5 ' x 1/8" column of 5% SE-30 on
Chromosorb W AW DMSC. Analytical results were obtained by
cutting and weighing Xerox copies of the chromatograms.
Preparative gas-liquid chromatography was carried out on a
Varian Aerograph 90-P thermal conductivity instrument using
a 18' X 1/4" column of 20% SE-30 on Chromosorb W. MCB grade
G2 silica gel or activity grade III Woelm basic alumina was
used for column chromatography.
All chemicals are reagent grade used as supplied unless
otherwise stated. Dioxane and tetrahydrofuran were dried
by distillation from lithium aluminum hydride and passage
over activity grade I Woelm basic alumina with subsequent
storage over calcium hydride under a nitrogen atmosphere.
8 3
1,3-Cyclopentadiene was prepared in the standard way from
dicyclopentadiene previously dried over magnesium sulfate
or 4A molecular seive. It was stored at Dry ice temperature
over sodium sulfate under nitrogen and used within two weeks,
Practical grade furan was washed with 5% sodium hydroxide,
dried over calcium sulfate, distilled from KOH, passed
through basic alumina (Woelm, Grade I) , and stored under
nitrogen. Diethylamine and butylamine were distilled from
lithium aluminum hydride or sodium hydroxide and passed
through a short grade I Woelm basic alumina column.
67
Acenaphthylene-1-carboxaldehyde (20) . — The procedure
2 f>
was a modification of that described by Buu-Hoi and Lavit.
Acenaphthylene (20.0 g, 130.mjnol, freshly sublimed), 15 ml
toluene, and dimethylf ormamide (14.5 g, 200 minol, dried
over 4-A sieve) were mixed under nitrogen. A portion of the
toluene (ca. 5 ml) was distilled to azeotrope away any water
present. The distillation head v/iis replaced with a reflux
condenser having a nitrogen T and drying tube at the top.
The flask v;as placed in a water bath at room temperature.
While stirring vigorously with a large blade stirring paddle,
phosphorous oxy chloride (28.0 g, 182 nmiol) was added dropwise
over a five-minute period. The solution v.'as warmed to 90°
and stirred at this temperature for 20 minutes as the mixture
darkened and partially solidified and then thinned to a dark
oil. The crude products v;ere cooled in an ice bath, and 20 ml
saturated sodium acetate added very slowly. After filtration
through Celite 545, the reaction mixture was extracted twice
with dilute hydrochloric acid and twice with water. The very
black organic solution was dried over calcium sulfate (anhy-
drous) and solvent removed. Volatile products were collected
by vacuum transfer of all material distilling below 180° at
0.1 mm of Hg. Careful fractional distillation gave unreacted
acenaphthylene (78-84°, 0.1 mm of Hg) followed by the desired
product 20^ (122-126°, 0.1 mm of Hg) as a stable yellow solid
contaminated with about 6% acenaphthylene. Recrystallization
from methylene chloride-pentane gave analytically pure ace-
naphthylene-1-carboxaldehyde (20) (5.7 g, 32 mmol, 24% yield)
G8
with the following properties: mp 55.5-57°; ir (KBr) :
3050, 2820, 1665, 1505, 1480, 1425, 1325, 1150, 1135, 975,
860, 770 cm"-'-; "'■H-nnir (CCl,,): t -0.05 (s, IH) , 1.79 (d, IH) ,
2.1-2.75 (m, 6H) ; mass spectrum: m/e 180 (M ).
Anal_. Calcd. for CisHeO: C, 86.65; H, 4.47. Found:
C, 86.50; K, 4.57.
The aldehyde 20^ formed a semicarbazone in ethanol which
after two recrystallizations from ethanol had mp 241-243°
(with decomposition, somewhat dependent on the rate of heating) ,
Lit., 240°, and under vacuum, mp 255-257°, Lit.,^^ 275°.
The aldehyde 20^ (0.1 g, 0.6 mii.ol) was oxidized with
chromic anhydride (0.25 g, 2.5 mmol) by refluxing 15 minutes
in 10 ml glacial acetic acid. Workup as described yielded
a small amount of material that was converted to 1,8-naph-
thanoic anhydride (0.02 g, 0.1 mmol, 20% yield) by acetic
anhydride. The crude final product was comparable by ir (ir
(KBr): 3060, 1770, 1735, 1580, 1305, 1015, 775 cm""^) to a
conuriercial sample (Aldrich) .
7,7-Dichlorodibenzo [a, c] bicycle [4.1.0] heptane (3_4) . — A
modified, procedure of Joshi, Singh, and Pande was employed. ^°
p
Cetrimide (Pfaltz and Bauer, Inc.) was used as the cationic
detergent (0.7 Cetrimide^ to 100 g phenanthrene) and the
reaction was run to completion by stirring 15 hours at room
temperature. Prior to recrystallization the product was
decolorized by eluting rapidly through a large silica gel
column with carbon tetrachloride. 3£ obtained (89.9 g, 58%
yield) was identical in all respects to that previously
69
characterized: mp 144-145", lit. 140.2" and 141.2
(melting occurs with decomposition ond. is a function of the
rate of heating) .
6-Chloro-5F-dibenzo [aj c] cyclohepten-5-ol (35^) . — 7,7-
Dichlorodibenzo [a, e] bicycle [4. 1.0] heptane (3£) (5.85 g, 22.4
mraol) was thermolyzed under nitrogen at 170±5 in an oil
bath for thirty minutes. The resultant oil was taken up in
100 ml of acetonitrile, and 130 ml of saturated sodium
bicarbonate solution was added. The two-phase reaction mix-
ture was stirred rapidly at room ter.-.perature for one hour as
a salt precipitated. After dilution with 100 ml of water,
the solution was extracted with three 75 ml portions of
methylene chloride. The combined organic extracts were dried
over anhydrous sodium sulfate and filtered. Solvent was
removed to yield 5.46 g (22.4 mmol , quantitative) of alcohol
35 suitable for further use.
Sublimation (150 , 0.15 mm of Hg) followed by grinding
under pentane gave colorless crystals of analytical purity:
mp 80.5-81.5°; uv: A (CaHjOIi) , 239 nm (e 41,000); ir
(melt): 3420, 3060, 1625, 1480, 1085, 755, 730 cm"-*"; ''•H-nmr
(CDCI3): T 2.3-2.9 (m, 8H) , 3.31 (s, IH) , 4.12 (d, J=6 Hz,
IH) , 7.26 (d, J=e Hz, IH) ; mass spectrum: m/e 242 (m"*") .
Anal. Calcd. for CisHiiCIO: C, 74.23; H, 4.68; CI,
14.60. Found: C, 74.35; H, 4.71; CI, 14.75,
70
6-Chloro-5/i'-dibenzo [qjC?] cyclohopten-5-one (_36) .--Acti-
vated manganese dioxide (Winthrop Laboratories, 30.0 g, 330
mmol) and 6-chloro-5^-dibenzo [aj<?] cyclohcpten-5-ol (35)
(5.27 g, 21.8 mmol) were stirred in 200 ml methylene chloride
at room temperature under nitrogen for one hour. Anhydrous
calcium sulfate was added, and the mixture was suction fil-
tered through Celite 545 . The residue was washed thoroughly
with 50 0 ml of ethyl acetate. Solvent v/as removed and the
oil column chromatographed on silica gel with carbon tetra-
chloride-methylene chloride (4:1). The crystalline product
(36) obtained after solvent removal (4.69 g, 19.5 mmol, 90%
yield) was suitable for further use.
Recrystallization from benzene-heptane gave analytically
pure 36: mp 98.0-98.8°, lit. ''■'•' "^^ 95.5-97.0° and 98°; ir
(KBr) : 1665, 1605, 1595 cm"-"", lit.'^"*-'^^ 1665, 1610, 1595 cm"-"";
H-nmr (CDCI3): t 2.0-2.7 (m) ; mass spectrum: m/e 240 (m"*") .
On contact with the face, 36^ is an annoying skin irritant.
6-Chloro-6 , 7-dihydro-5tf-dibenzo [a, g] cyclohepten-5-one
(37^) .--Catalytic hydrogenation of 6-chloro-5W-dibenzo [Qj c] -
cyclohepten-5-one (3£) (4.59 g, 19.1 mmol) was carried out
over 5% palladium on carbon (0.75 g) in 75 ml ethyl acetate
containing one milliliter of glacial acetic acid using a
8 5
standard atmospheric pressure hydrogenation apparatus.
Hydrogen (468 ml, uncorrected for solvent vapor) was taken
up in 3.4 hours at one atmosphere pressure and 24 . The
reaction mixture was filtered through sodium carbonate
(anhydrous) , washed with ethyl acetate, and solvent removed.
71
The crude product mixture consisted of 20% unreacted starting
material 3£, 67% desired product 37_, and 13% of a product
formed on further liydrogenolysis , 6 , 7-dihydro-5i7-dibenzo-
[Qj c] cyclohepten-5-one (3_9 ) . The desired product 37_ con-
taminated with 16 V starting material (3.57 g) eluted as the
first major component from a silica gel column with carbon
tetrachloride. Recrystallization from ethanol-water yielded
37 (3.08 g, 12.7 nmol , 76% yield) , and a portion of starting
material v/as recovered (0.52 g) .
Analytically pure 3_7 v/as obtained after a second
recrystallization from ethanol-water: mp 89-90 ; uv: X
■^ ^ max
(CallsOH) , 305 nra (e 1,600), 238 (24,000); ir (KBr) : 3060,
3020, 2920, 1695, 1595, 1205, 920, 800, 795, 655 cm""*-;
H-nmr (benzene-dt ) : t 2.3-2.6 (m, 2H) , 2.7-3.2 (m, 6H) ,
4.62 (t, J=7.5 Hz, 111), 7.05 (d, J=7 . 5 Hz, 2H) ; H-nmr
(acetone-ds) : x 2.1-2.7 (m, 8H) , 4.11 and 7.03-6.29 (ABX
pattern, v - x 6.81, v^ = x 6.48, v = x 4.11, J = 13.5 Hz,
J^j, = 9.0 Hz, Jgj^ =4.5 Hz, 3H) ; •'"H-nmr (CCIO : x 2.3-2.9
(ra, 8H) , 4.52 and 6.6-7.1 (unusual ABX pattern, v = x 6.84,
V,- = X 6.61, v^ = X 4.52, J_^ = 13.5 Hz, J^^ = 12. Hz,
B 'X AB ' AX
Jgj^ = 3. Hz, 3H) ; mass spectrum: m/e 242 (M"*") , 180 (M+ -
COCl, major peak) .
Anal. Calcd. for CisHnClO: C, 74.23; H, 4.68; CI,
14.60. Found: C, 74.02; H, 4.73; CI, 14.53.
72
6 ,7-Diliydro-r>//-dibenzo [a,c] cyclohepten-5-one (39) . —
a) This material v;as eluted as the second major component
off the silica gel column with carbon tetrachloride con-
tainin>.j increasing amounts of methylene chloride as eluent.
39 (0.33 g, 1.6 nuviol , 10% yield) was obtained after recrystal-
lization from metlianol-water . Sublimation gave analytically
pure material: lap 85.0-85.8 , lit. 85-86 .
b) 6"Chloro--5//-dibenzo [flj c] cyclohepten-5-one (_36) (0.175
g, 0.729 nuiiol) was catalytically reduced on 5% palladium on
charcoal (0.034 g) in 12 ml absolute ethanol containing
anhydrous sodium acetate (0.150 g, 1.83 mmol). Two equiva-
lents of hydrogen (35.7 ml at one atmosphere and 24 ) were
taken up in 4 0 minutes at which point hydrogenation ceased.
The reaction mixture was filtered, and solvent removed.
Sublimation (80°, 0.15 mm of Hg) gave analytically pure 39^
(0.144 g, 0.547 nmiol , 82% yield) identical to that obtained
by procedure a) : mp 85-86 , lit, 85-86 ; ir (melt) :
3060, 2930, 1G75, 1595, 1445, 1265, 750 cm""^, lit.'^^ v^^^
1678 cm" ; ''"Il-nmr (CDCI3): t 2.2-2.8 (m, 8H) , 7.00 (s, 4H) ;
H-nmr (benzene-de ) : t 2.05-2.3 (m, IH) , 2.7-3.2 (m, 7H) ,
7.2-7.7 (m v/ith AA'BB' pattern, 4H) ; mass spectrum: m/e 208
(m"^) , 207 (major peak), 180 (M'^'-CO) .
73
Mixtures of 6-Chloro-6 ,7-dihydro-5//-dibenzo [c;, <?] cyclo-
hepten-5-one (32) and 6 ,7-Dihydro-5ff-dibenzo [a^ c] cyclohepten-
5-one (39^) from Catalytic Reduction. — 6-Chloro- 5//-dibenzo-
[aj c] cyclohepten-5-one {36_) (0.112 g, 0.47 nunol) and 0.05 g
of 5% Pd on carbon were placed in 10 ml of solvent and
hydrogenated until 11.4 ml of the hydrogen (0.51 irauol) had
been taken up. The reaction products were worked up as
before (filtration and solvent removal) , and the ratio of
chloroketone 31^ to ketone 3£ determined by mar. Thco following
results were obtained:
Solvent
Mole
Reduction
Ratio
Time
37/39
(minutes)
Ethanol 0.3 7
Ethyl acetate
(1% HOAc) 5.2 35
HOAc (glacial) 3.0 20
1:1 Benzene/cyclohexane 0-9 70
Methyl propionate 3.5 4 0
5//-Dibenzo [aj e]cyclohepten-5-one (3£) . — To a solution
of anhydrous lithium chloride (13.0 g, 4 00 mmol) in 200 ml
dimethylformamide (dried over 4A sieve) was added 6-chloro-
6 ,7-dihydro-5i:?-dibenzo [a, c] cyclohepten-5-one (37^) (3.03 g,
12.5 mmol), and the solution was stirred at reflux under
nitrogen for fifteen hours. The solvent was distilled off
until lithium chloride began to precipitate. The pot residue
was diluted with 300 ml of water and extracted with three
40 ml portions of methylene chloride. The organic extracts
74
were combined and dried over anhydrous magnesium sulfate.
Filtration and solvent removal left a viscous oil from
which the last bit of dimethylformamide was removed in
vacuo. The oil was column chroma tographed on silica gel
witli carbon tetrachloride containing increasing amounts of
chloroform. Crystalline 38^ was obtained after solvent
removal (2.20 g, 10.7 mmol, 85% yield). Sublimation (120 ,
0.2 mm of Hg) gave white crystals (1.93 g) with the following
properties: mp 83-84. 5°, lit.^^ 83-85°; ir (KBr) : 3060,
3030, 1640, 1590, 1405, 1295, 790, 785, 770, 755, 740, 730,
1 86 1
570 cm" (identical to a published spectrum ); H-nmr (CDCI3)
T 1.9-2.8 (m, 9H) , 3.35 (d, J=12 IIz , III); mass spectrum:
m/e 206 (m"*") , 178 (m"^-CO, major peak).
Preparation of Tosylhydrazonos . — Benzaldehyde free
tropone was prepared by the hydrolysis procedure of Harmon
87
and Coburn and converted to the tosylhydrazone as pre-
A "7
viously described. 4 ,5-Benzotropone tosylhydrazone (53)
was synthesized in the reported manner, as were phenalen-1-
one tosylhydrazone (19^) and the analogous benzenesulfonyl-
25
hydrazone of phenalen-1-one. New tosylhydrazones were
prepared in the conventional way by stirring equal molar
quantities of tosylhydrazide and the aldehyde of ketone in
absolute ethanol (1 g/30 ml) with a drop of concentrated
sulfuric acid for 15 to 20 hours. The following products
were obtained after recrystallization from ethanol:
5tf-Dibenzo [a, c?] cyclohepten-5-one tosylhydrazone (4_1) / 94%
75
yield; mp 192-195° (with decomp.); ir (KBr) : 3205, 3060,
1631, 1595, 1170, 1082, 760, 740, 670, 610 cm""'-; "'•H-nmr
(DMSO-dg): T 0.39 (bs , IH) , 2.1-2.8 (ra, 12H) , 2.85-3.4 (d
of doublets, 2H) , 7.67 (s, 3H) ; mass spectrum: m/e 374
(M ), 190 (major peak); Anal. Calcd. for C22H18N2O2S:
C, 70.57; H, 4.85; N, 7.48; Found: C, 70.42; H, 4.96;
N, 7.25; Phenanthrene-9-carboxaldehyde tosylhydrazone (45),
95% yield; mp 161-167° (with decomp.); ir (KBr): 3190,
3070, 1640, 1600, 1500, 1455, 1170, 935, 755, 580 cm"^;
H-nmr (DMSO-de): t -1.7 (bs, IH) , 1.0-1.5 (m, 4H) , 1.8-2.7
(m, lOH) , 7.67 (s, 3H) ; mass spectrum: m/e 374 (m"*") , 190
(major peak); Anal. Calcd. for C22H18N2O2S: C, 70.57;
H, 4.85; N, 7.48; Found: C, 70.66; H, 4.90; N, 7.40; Ace-
naphthylene-1-carboxaldehyde tosylhydrazone (21), 95% yield;
mp 158-159°; ir (KBr): 3190, 3060, 1595, 1425, 1350, 1305,
1165, 1050, 915, 810, 775, 665, 600, 560, 545, 530 cm~^;
H-nmr (acetone-dg ) : t -0.18 (bs, IH) , 1.64 (d of doublets,
IH), 1.78 (s, IH); 1.95-2.8 (m, lOH) , 7.70 (s, 3H) ; mass
spectrum: m/e 164 (major peak); Anal. Calcd. for C20H16N2O2S:
C, 68.95; H, 4.63; N, 8.04; Found: C, 69.00; H, 4.72; N, 8.08,
Preparation of Sodium Salts of Tosylhydrazones . — The
sodium salts were prepared in the dry box under a nitrogen
atmosphere, by dissolving the tosylhydrazone in dry tetra-
hydrofuran (ca. 2 g/50 ml) and adding 1.1 equivalents of
sodium hydride (57% in mineral oil; Alfa Inorganics) slowly
with stirring. Stirring was continued for an additional one
hour. An equal volume of spectrograde pentane was added,
and the resulting precipitate filtered, dried under vacuum.
76
and stored in a dark bottle in the dry box. The preparation
was assumed to be quantitative and further reactions are
based on weight of tosylhydrazone consumed.
Thermolysis and Photolysis of Aldehyde and Ketone
Tosylhydrazone Sodium Salts. --Thermolyses were carried out
in a sealed tube (a 3 oz or 1 oz Fisher-Porter Aerosol
Compatibility Tube) containing a magnetic stirring bar.
The tube was well flushed with nitrogen and charged in the
dry box. The tliermolysis temperature was maintained within
±5 in a preheated silicone oil bath. After cooling to room
temperature the tube was vented to a gas buret that permitted
a determination of nitrogen evolution. "Hot tube" pyrolyses
for gas phase generation of carbenes were performed with a
p
Pyrex apparatus modeled after that employed for phenyl-
carbene-cycloheptatrienylidene generation. A hot zone 16 cm
in length was maintained at the desired temperature (+20 )
with a Chrome resistance wire (22 gauge) controlled with a
variac. The tube was evacuated with an Edwards High Vacuum,
Inc. , model ES 330 high vacuum pump with a displacement of
11.8 CFM. A nitrogen flow measured at atmospheric pressure
was maintained during addition to give a pressure of 1 to 2
mm of Hg. Dry firebrick (dried under high vacuum at 250
overnight) was used as an inert support and diluent for the
anhydrous salts. The firebrick was retained in the tube by
a glasswool mat located about 2/3 of the way down the hot
zone. A salt was added from a solid addition tube (charged
in the dry box) over a half -hour period, and products were
77
condensed in a trap immersed in liquid nitrogen. For small
scale photolyses (0.1-0.4 g) , an apparatus having two Pyrex
tubes sealed into a small volume cooling jacket 3 cm apart
was employed. A 550 W Hanovia "High-Pressure Quartz Mercury-
Vapor Lamp" was placed in one tube, and the other tube of
35 ml maximum volume was used as the reaction vessel. An
electronic stirrer was inserted through one of two ground
glass inlets to the reaction vessel. A nitrogen atmosphere
was maintained via the other inlet. For room temperature
photolyses, the apparatus was immersed in a water bath and
a tap v/ater flow through the cooling jacket controlled the
temperature at 30±5 . For low temperature photolyses, the
apparatus was immersed in a Dry- ice-methanol bath and methanol
cooled with Dry ice was circulated through the cooling
jacket by a magnetic drive centrifugal pump. The temperature
was thus held at -60+5°.
Preparative-scale Photolysis of Diazo-2 , 3 , 4 , 5-tetra-
phenylcyclopentadiene in Benzene at 100° .--Diazo-2 , 3 ,4,5-
8 8
tetraphenylcyclopentadiene (0.50 g, 1.25 mmol) and 40 ml
benzene (fresh bottle) were added to a 3 oz Fisher-Porter
Aerosol Compatibility Tube in the dry box. The tube was
sealed under nitrogen and heated in a boiling water bath
(100±5 ) with external photolysis (550 W Hanovia, Pyrex
filter) . Photolysis was discontinued after six hours at
greater than 90% completion (tic (benzene) showed a trace of
the diazo starting material remaining) . Solvent was removed
78
under reduced pressure and the principal product, 1,2,3,4,5-
pentaphenylcyclopentadiene (16^) (0.39 g, 0.88 nunol, 68%
yield) , isolated by crystallization from ethanol. Recrystal-
lization from xylene gave _16 as a white solid with the fol-
lowing properties: mp 248-252°, lit."'-^'^^ 244-246°, 247°,
254°; ir (KBr) : 3080, 3050, 3020, 1595, 1570, 1484, 1440,
1070, 1030, 910, 835, 785, 770, 755, 720, 695, 680, 550 cm~^
(identical to the published spectrum); uv: X (cyclo-
hexane) 340 nm (log e 4.01), 268 (4,34), 245 (4.44), lit.^^^
^raax^^^°^°^®^^'^^^ 338-340 nm (log e 4.00), 269 (4.35), 245
(4.44). ,
Small-scale Photolysis of Diazo-2 , 3 ,4 , 5-tetraphenyl-
cyclopentadiene in Benzene at 100°. — Diazo-2, 3, 4 ,5-tetra-
phenylcyclopentadiene (0.035 g, 0.090 mmol) and 7 . 3 ml
benzene were placed in a 1 oz compatibility tube and photo-
lyzcd (550 W Hanovia, Pyrex filter) 5 hours while heating in
a boiling water bath (100+5°) . The light path length was
half that of the preparative photolysis, and the cell was
half as wide and 3/4 as high,., making the rate of photolytic
rearrangement five times as great with an equivalent rate of
thermal rearrangement. The photolysis went to completion,
and on cooling three products were detected by tic (cyclo-
hexane/15% toluene) and glc (5% SE-30, 10' x 1/8", 235°),
1,2,3,4,5-pentaphenylcyclopentadiene (_16) (R =47 min,
identical to material previously prepared by glc (coinjec-
tion) and tic), 1 , 2 , 3 , 4-tetraphenyl-7ff-benzocycloheptene (9)
79
(R =52 min, identical to authentic material supplied by
T. Mitsuhashi) , and 5 , 6 ,7 , 8-tetraphenyl-7/y-benzocycloheptene
(10) (R =59 min, identical to Mitsuhashi 's authentic material)
in a mole ratio of 47:10:43.
Pyrolysis of Tropone Tosylliydrazone Sodium Salt in the
Presence of 2 , 3 , 4 , 5-Tetraphenylcyclopentadienone . — Tropone
tosylhydrazone sodium salt (0.033 g, 0.128 mmol) and 2,3,4,5-
tetraphenylcyclopentadienone (0.10 g, 0.26 mmol) were dis-
solved in 11 ml benzone, placed in a 1 oz compatibility tube
under nitrogen, and heated in a boiling water bath (100+5 )
for five hours. Gas chromatography (5% SE-30, 10' x 1/8",
235°) showed, besides a substantial amount of unreacted
2, 3 ,4 , 5-tetraphenylcyclopontadienone (R =37 min), the two
7 -benzocycloheptones , 1 , 2 , 3 , 4-tetraphenyl-7//-benzocyclo-
heptene {9) and 5 ,6 , 7 , 8-tetraphenyl-7r/-benzocycloheptene
(10) (identical by tic (benzene) and glc with authentic
samples supplied by T. Mitsuhashi) , in a mole ratio of
0.20:0.80. No 1 , 2 , 3 , 4 , 5-pentaphenylcyclopentadiene (16)
was detected.
Photolysis of 1 , 2 , 3 , 4-Tetraphenyl-7//-benzocycloheptene
(9_) and 5 , 6 , 7 , 8-Tetraphenyl-7/f-benzocycloheptene (10) . — A
dilute solution of 1 , 2 , 3 ,4-tetraphenyl-7i:/-benzocycloheptene •
(9_) and 5 , 6 , 7 , 8-tetraphenyl-7//-benzocycloheptene (1£) in
8 ml benzene was prepared from authentic samples supplied by
T. Mitsuhashi. Gas chromatography (5% SE-30, 10' x 1/8",
235°) indicated a 1.85:1 molar ratio (^ to 1£) . The solution
80
was photolyzed (550 W Hanovia, Pyrex filter) 4 hours at
100+5 in a 1 oz compatibility tube, and again analyzed by
gas chromatography. A molar ratio of 1.5:1 (2:1£) with slight
peak broadening was observed. Since the peaks overlap by
about 20% on tlio chromatogram, the results are identical
before and after photolysis within the experimental error.
Thus the photolysis products are stable to the reaction condi-
tions, and gas chromatography gives a good estimate of the
amount of each isomer formed.
Room Temperature Photolysis of Diazo-2 , 3 , 4 , 5-tetraphenyl-
cyclopentadiene in Benzene. — Diazo-2 ,3,4, 5-tetraphenylcyclo-
pentadiene (0.30 g, 0.75 mn.ol) was photolyzed (450 W Hanovia,
Pyrex filter, lov; conversion) 1 hour in 250 ml benzene using
a preparative reactor with a water-cooled Hanovia immersion
well. Tic (cyclohexane/15?, toluene) and glc (5% SE-30, 10' x
1/8", 235 ) comparisons with authentic samples (prepared by
T. Mitsuhashi) demonstrated the presence of 1, 2, 3 ,4-tetra-
phenyl-7//-benzocycloheptene (9) and 5 , 6 ,7 , 8-tetraphenyl-7/^-
benzocycloheptene (1£) in a 1:1 molar ratio. No 1,2,3,4,5-
pentaphenylcyclopentadiene (]^) could be detected.
Pyrolysis of Phenalen-1-one Tosylhydrazone Sodium Salt
(19 ' ) in Dioxane. — Phenalen-1-one tosylhydrazone sodium salt
(19^') (0.29 g, 0.78 mmol) was weighed into a Fisher-Porter
Compatibility Tube in the dry box under nitrogen and 40 ml
dry dioxane added. The tube was placed in a preheated
silicon oil bath, and the reaction mixture was stirred for
81
25 minutes at 160°. The mixture was cooled and a portion
(2.5%) subjected to quantitative gas chromatography with
anthracene (7.3 x 10 g) added as a standard. Phenalene
(23) (0.0090 g, 0.054 mmol , 6.9% yield) was the only signifi-
cant (>0.1%) volatile product detected by gas chromatography
(5% SE-30, 10' X 1/8", 125°). This product had a retention
time (R =15.7 min) identical to that of authentic material
28
prepared according to Boekelheide and Larrabee. Tic
(pentane or CCl^) also indicated that the major product was
identical to the authentic phenalene (23_) with an nmr spectrum
[■"■H-nmr {CC1^): T 2.5-3.3 (m, 6H) , 3.52 (d of t, IH) , 4.12
27
(d of t, 111), 6.05 (bs, 2H)] as shown in the literature.
No trace of 1-methylacenaphthylene (26^) or an acenaphthyl-
carbene dioxane insertion product 27^ ^^^ noted in the chroma-
togram (limit of detection better than 0.01%). Another
portion of the reaction mixture was evaporated to dryness
at 60° under reduced pressure, taken up in benzene, and
chromatographed (benzene) on a Woelm alumina column (Grade
III) . Phenalene (23^) was separated at the solvent front
followed by peropyrene (2£) (9.4 x 10~ g, 5.8 x 10~ mmol,
0.75% yield) which was quantitated by uv-vis spectrophotometry
31
in benzene. Due to its carcinogenic nature no attempt
was made to isolate pure peropyrene (2_4) , but properties
of dilute solutions left little doubt as to the identity of
this hydrocarbon. The uv-vis spectrum was consistent with
that reported: X (benzene) 443, 416, 393, 373, 326 nm
"^ max
(log e 5.20, 4.93, 4.56, 4.18, 4.87), lit.^^ X^^^ 443.5,
82
41b. 5, 393, 371, 352, 326 nm (log e 5.22, 4.90, 4.44, 3.98,
3.48, 4.77). Tic (benzene or chlorobenzene) and glc (5%
SE-30, 5' X 1/8", 300°, R =19 min) were identical to those
of authentic 2£ prepared by the method of Aoki. A small
amount of the trivial phenalen-1-one azine (22^) was also
isolated from the column as a very slow moving red band.
The azine was identical (tic, uv-vis, nmr) to authentic
25
material prepared by the method of Hunig and Wolff.
Pyrolysis of Acenaphthylene-l-carboxaldehyde Tosylhydra-
zone Sodium Salt (2_1 ' ) in Dioxane. — Acenaphthylene-1-carbox-
aldehyde tosylhydrazone sodium salt (2j_' ) (0.27 g, 0.73 mmol)
in 4 0 ml dry dioxane was heated 20 minutes at 150 in a
sealed tube under conditions similar to those employed for
thermolysis of the ketone tosylhydrazone sodium salt 19^' .
The solution was cooled and nitrogen evolution measured:
10.3 ml (24°, 1.00 atm uncorrected for solvent vapor, ca .
57% yield) . The substantial quantity of white solid present
in the reaction mixture was filtered from the solution and
dissolved in 100 ml chloroform. The chloroform solution was
extracted three times with water to remove any sodium toluene-
sulfinate present. The solution was dried and solvent volume
reduced until clouding occurred. The solid that crystal-
lized from the solution at 0° was collected and recrystal-
lized from chloroform. The compound was identified as the
trivial diazocyclization product, 7tf-acenaphtho [1 , 2-(?] -
pyrazole (25): mp 238-241°, lit."^^ 239°; ir (KBr) : 3040,
83
2900, 1470, 1405, 1290, 1170, 1035, 980, 820, 770, 620 cm""'-;
H-nmr (DMSO-de): x 1.9-2.4 (m) . The soluble reaction
products were quantitatively determined by gas chromatography
with a weighed standard added and were isolated by prepara-
tive gas chromatography (20% SE-30, 18' x 1/4", 225°).
1-Methylacenaphthylene (26_) (0.008 g, 0.05 mmol, 7%) was
the major product (R. =15 rain) isolated and had properties
consistent with those reported: ir (film): 3040, 2920,
2850, 1480, 1460, 1450, 1430, 840, 810, 770 cm"-*-, lit.^^,
838, 805, 770 cm"""-; "''H-nmr (CClw): t 2.3-2.7 (m, 611), 3.42
(bs, IH) , 7.63 (d, J=2 Hz, 3H) , lit,"^^, x 7.65 and 7.63;
mass spectrum: m/e 166 (m"*", 61), 165 (m"''-1, 100), lit."^^,
166 (52) , 165 (100) . The minor product (R^=23 min) is
tentatively identified as the dioxane insertion product 2_7
of acenaphthylcarbene (0.006 g, 0.024 mmol, 3% yield) from
its nmr spectrum: H-nmr (CClu): x 2.2-2.65 (m, 6H) , 3.30
(bs, IH) , 6.1-6.6 (m, 7H) , 7.1-7.3 (ca. d, 2H) . No evidence
for any phenalene 2_3 or peropyrene 2_4 could be detected by
gas chromatography with coinjection of authentic samples.
"Hot Tube" Pyrolysis of Phenalen-1-one Tosylhydrazone
Sodium Salt (19^' ) • --Phenalen-1-one tosylhydrazone sodium
salt (19^') (0.46 g, 1.25 mmol), was gound in the dry box
with approximately one gram of dry firebrick and placed in
a solid addition tube with a nitrogen inlet. The salt 19 '
was dropped down the short pyrolysis tube at 410 in 1/2
hour. Products were condensed in a liquid nitrogen trap
containing a glasswool pad to break aerosols. After warming
84
to room temperature under nitrogen, products were dissolved
in 100.0 ml benzene (spectrograde) and quantitatively
analyzed by gas chromatography (10* x 1/8", 5% SE-30, 160°)
with trans-stilbene as a standard. Phenalene (23) (R =14 min,
identical with authentic material^^ and that isolated pre-
viously as determined by coinjection, 1.1 x lo"^ g, 0.0065
iiunol, 0.53% yield) was the major product, and 2,3-dihydro-
phenalene 28 (R^=ll min, 8.5 x lO"^ g, 5. x lo""* mmol , 0.05%
yield) was a minor product which was characterized by uv
spectrophotometry (uv: A^^^(EtOH) 228 and 289 nm, qualita-
tively identical to the spectrum shown in the literature^^) .
Five other components present in slightly lesser amounts
were also indicated by gas chromatography. Glc at 300° on
a 5-foot column showed peropyrene (24^) as the major product
from the pyrolysis. By uv-vis spectrophotometry (benzene)
of the crude product mixture, peropyrene (24:) (0.0078 g,
0.025 mmol, 3.8% yield) was also detected (identical by glc,
tic, and uv-vis with authentic material^° and that isolated
previously) . No 1-methylacenaphthylene (26) was present to
a limit of detection of 0.005% by gas chromatography with
coinjection of product mixtures from pyrolyses of acenaph-
thylcarbene.
"Hot Tube" Pyrolysis of Phenalen-1-one Benzensulfonyl-
hydrazone Sodium Salt.— The benzenesulfonylhydrazone sodium
salt of phenalen-1-one (0.30 g, 0.84 mmol) ground with 1.2 g
of dry firebrick was dropped down the hot tube at 360° in
40 minutes. The pyrolysis products were isolated from the
85
trap and dissolved in carbon tetrachloride. A qualitative
comparison of the products with those obtained on pyrolysis
of the tosylhydrazone salt of this ketone by gas chroma-
tography at 16 0 indicated only two common products, phenalene
(23) and 2 ,3-dihydrophenalene (2£) . The five minor unidenti-
fied components which are different in the two mixtures must
result from the benzenesulfonyl or tosyl portion of the mole-
cule. Coinjection of commercial samples suggested the nature
of the tv/o major compounds of these groups: the shortest
retention time material was thiophenol (or thiocresol) and
the longest retention time material was phenyl disulfide
(or toly disulfide) . Coinjection of the two crude product
mixtures produced a new compound with a retention time
intermediate between phenyl disulfide and toly disulfide
(likely, the unsymmetrical disulfide), but only phenalene
(23) and dihydrophenalene (28_) superimposed on the chromato-
gram. Peropyrene (2_4) was also shov;n to be a common product
by glc at 300°.
"Hot Tube" Pyrolysis of Acenaphthylene-1-carboxaldehyde
Tosylhydrazone Sodium Salt (21'). --Acenaphthylene-1-carbox-
aldehyde tosylhydrazone sodium salt (2_1 ' ) (0.45 g, 1.21 mmol) ,
was pyrolyzed and products isolated and quantitated under
conditions as nearly identical as possible to those employed
for the hot tube pyrolysis of the ketone tosylhydrazone salt
(!£' ) (i.e., 410 , firebrick support, 1/2 hour addition, gas
chromatography with stilbene as standard, and quantitative
uv-vis spectrophotometry in benzene) . Phenalene (23)
86
(0.0066 g, 0.040 mmol , 3.3% yield), l-nethylacenaphthylene
(26) (0.0036 g, 0.022 irjnol, 1.8"o yield, identical by coinjec-
tion with material previously characterized) , and toluene-
sulfinate reduction products as observed from pyrolysis of
the aromatic carbene 1£' were detected by gas chromatography
at 160°. Pcropyrene (24^) (0.0105 g, 0.0322 mmol, 5.3% yield)
was also present as shown by gas chromatography (300 ) and
uv-vis spectrophotometry.
9- (2 , 4 ,6-Cycloheptatrien-l-yl)phenanthrene (42^). --a) 5/y-
Dibenzo [a, c?] cyclohepten-5-one tosylhydrazone sodium salt
(41^') (0.16 g, 0.40 mmol) was heated with stirring in 35 ml
of reagent grade benzene for 2 hours at 125 in a sealed
tube. A quantitative evolution of nitrogen (9.7 ml at 24
and 1.00 atmosphere, 0.40 mmol) resulted, and on filtration
a quantitative yield of sodium toluenesulf inate dihydrate
(0.088 g, 41 mmol) vv'as collected with ir spectrum (KBr)
84
identical to that reported. The oil obtained after solvent
evaporation (0.102 g, 0.38 mmol, 95% yield) was primarily
the single material, 9- (2 ,4 ,6-cycloheptatrien-l-yl)phenan-
threne (£2)^ by nmr and tic (trace amounts of H-shift isomers
and cycloheptatriene to toluene rearrangement products are
apparently the only impurities) . Two successive preparative
layer chromatography separations (pentane , 3 elutions)
yielded £2^ as the most rapidly moving, major component.
Recrystallization of the solid obtained from hexane and then
from methanol gave analytically pure 4_2 (0.025 g, 0.093 mmol,
23% yield): mp 127-128°; uv : X (iso-octane) , 348 nm
max
87
(e 390), 341 (sh, 340), 339 (370), 332 (540), 324 (sh, 520),
297 (12,400), 285 (11,600), 276 (16,600), 254 (61,300), 247
(53,600), 222 (31,400); ir (KBr) : 3060, 3030, 3010, 2850,
1600, 1490, 1450, 1430, 1255, 1145, 950, 900, 885, 770, 745,
730, 720, 710, 700, 620, 415 cm""^; "^H-nmr (CDCI3): x 1.2-1.5
(m, 2H) , 1.8-2.7 (m, 6H) , 3.15-3.3 (narrow d of doublets,
2H) , 3.5-3.85 (m, 2H) , 4.2-4.5 (d of doublets, 2H) , 6.4-6.7
(broad t, IH) ; mass spectrum: m/e 268 (m"^, 100), 267 (m'*"-1,
68) .
Anal. Calcd. for C21H17: C, 93.99; H, 6.01. Found:
C, 93.73; H, 6.11.
b) Room temperature photolysis of 5ff-dibenzo [a^ c] -
cyclohepten-5-one tosylhydrazone sodium salt {^' ) (0.10 g,
0.25 mmol) for 50 minutes in 30 ml of benzene produced
after filtration and solvent evaporation a yellow oil from
v/hich, after preparative layer chromatography (pentane, 3
elutions) , 9- (2 ,4 ,6-cycloheptatrien-l-yl)phenanthrene (42)
(0.035 g, 0,13 mmol y 52% yield) was isolated. Recrystal-
lization (hexane) gave pure 4_2 with physical and spectral
properties identical to those of 4_2 formed by thermolysis
of the salt (see (a} above ) .
c) . Low temperature photolysis at -60 of 5^-dibenzo-
[a, c] cyclohepten-5-one tosylhydrazone sodium salt (41 ' )
(0.10 g, 0.25 mmol) in 27 ml of a 1:2 solution of benzene-
tetrahydrofuran was carried out for 50 minutes ..at room
temperature and worked up in a similar manner. 9- (2,4,6-
-5
Cycloheptatrien-1-yl) -phenanthrene (42) (3.-10. x 10 g.
88
1.3 X 10~^ nunol, 0.04-0.13% yield) was isolated by prepara-
tive layer chromatography (pentane, 3 elutions) and quanti-
tatively determined by uv spectroscopy.
Low Temperature Photolysis of 5//-Dibenzo [a,c] cyclohep-
ten-5-one Tosylhydrazone Sodium Salt (41') in Tetrahydro-
furan. — 5//-Dibenzo [a, <?] cyclohepten-5-one tosylhydrazone
sodium salt (4_1 ' ) (0.10 g, 0.25 mmol) was photolyzed 1 hour
at -60° in 15 ml of dry tctrahydrofuran . The yellow reaction
mixture was warmed to room temperature and filtered. Solvent
was evaporated. An nmr spectrum of the residue indicated a
low yield of chloroform soluble products, predominantly if
not completely aromatic proton resonances were observed
(<10% phenanthryl) ; tic (cyclohexane-benzene , 2:1) showed
numerous components with a good deal of streaking. Isola-
tion and characterization of these minor compounds was not
attempted.
Low Temperature Photolysis of the Sodium Salt of 5H-
Dibenzo[a,c]cyclohepten-5-one Tosylhydrazone (41') in the
Presence of Styrene . — 5^-Dibenzo [a, c] cyclohepten-5-one
tosylhydrazone sodium salt {Al_' ) (0.16 g, 0.40 mmol) was
photolyzed 1 hour at -60° in 15 ml of dry tetrahydrofuran
containing styrene (2.50 g, 24.0 mmol, inhibitor removed by
putting through Grade I VJoelm alumina) . The solution was
warmed to room temperature and suction filtered. The solvent
was evaporated and styrene removed in vacuq^ at room tempera-
ture. Nmr and tic of the residue were very similar to those
89
of the product mixture obtained from photolysis in the
absence of styrene (no vinyl protons in the nmr to a limit
of detection of -2-i) . Attempted sublimation (4 hours, 100 ,
0.15 mm of Hg) failed to transfer any material to the cold
finger.
Low TemiDerature Photolysis of the Sodium Salt of 5H-
Dibenzo [aj e] cyclohepten-5-one Tosylhydrazone (4_1 ' ) in the
Presence of Dimethyl Fumarate. — 55-Dibenzo [a, a] cyclohepten-
5-one tosylhydrazone sodium salt (4_1 ' ) (0.212 g, 0.538 mmol)
was photolyzed 1.5 hours at -60 in 30 ml of a saturated,
dry tetrahydrofuran solution of dimethyl fumarate (2.50 g,
18.0 mmol, recrystallized from chloroform-hexane) . The
solution was allowed to come to room temperature and suction
filtered. The solvent was removed and dimethyl fumarate
sublimed av/ay at 40° (0.2 itub of Hg , overnight). The H-nmr
spectrum of tlie residue showed no vinyl protons to a limit
of detection of -2% and was similar to that of the reaction
mixture obtained on photolysis in the absence of dimethyl
fumarate; tic, also, gave no indication of dimethyl fumarate
reaction products.
Low Temperature Photolysis of Sff-Dibenzo [a, g] cyclohep-
ten-5-one Tosylhydrazone Sodium Salt (4_1 ' ) in the Presence
of 1 .3-Cyclopentadiene. — 5W-Dibenzo [a^ a] cyclohepten-5-one
tosylhydrazone sodium salt (41') (0.20 g, 0.50 mmol) was
photolyzed 40 minutes at -60 in 20 ml dry tetrahydrofuran
8 3
containing freshly prepared cyclopentadiene monomer
90
(5 ml, 75 mmol) . The reaction mixture was allov;ed to warm
to 5 , and solvent was removed under reduced pressure.
(The last trace of dicyclopentadiene was removed in vacuo.)
The residue was taken up in cyclohexane and column chromato-
graphed on silica gel (cyclohexane) . A single component,
2 4
endo- 2 , 3- (d-biphenylenyl) -tricyclo 13 . 2 . 1. 0 ' ]oct-6-ene
(43) (0.094 g, 0.37 mmol, 73% yield), eluted from the
column. Molecular distillation (110 , 0.2 mm of llg) yielded
a pure, colorless liquid with the following properties:
uv: X ^ (iso-octane) , 308 nm (c 2,300), 273 (4,700), 257
(5,100), 248 (7,700), 239 (8,200), 221 (14,000); ir (film):
3060, 3030, 2970, 2930, 2860, 1600, 1490, 1445, 1330, 1245,
1045, 1020, 890, 850, 790, 745, 740, 725, G95, 675, 620 cm""'-;
•""H-nmr (CCl..): t 2.0-2.3 (m, 211), 2.4-2.7 (m, 2H) , 2.75-3.05
(m, 4H) , 3.95 (ca. t, 211), 6.61 (bs. Hi, IH) , 6.89 (bs, H5,
IH) , 7.49 (d, H3, J^ 4=2.8 Hz, IH) , 7.73 (d , H8 , J =6.8 Hz,
IH) , 8.10 (d, H8, IH) , 9.39 (d of doublets, H4 , J ^=2.8 Hz,
J^ 5=2.6 Hz, IH) ; mass spectrum: m/e 256 (m"*", 100), 216
(75) , 192 (52) .
Anal. Calcd. for C20H16: C, 93.71; H, 6.29. Found:
C, 93.50; H, 6.41.
Low Temperature Photolysis of 5ff-Dibenzo [g, c] cyclohep-
ten-5-one Tosylhydrazone Sodium Salt (4_]^' ) with Subsequent
Addition of 1 . 3- Cyclopentadiene . --a) 5//-Dibenzo [a, c] cyclo-
hepten-5-one tosylhydrazone sodium salt (4J^' ) (0.103 g,
0.260 mmol) was placed in 25 ml dry tetrahydrof uran. The
91
solution was cooled to -60 and photolyzed 7 minutes v;ith
rapid stirring. The light was extinguished, and 1,3-cyclo-
pentadiene (7 ml, 100 mniol) at -78 was added within 3
seconds. The solution was allowed to v/arm to 5^, and solvent
was partially removed under reduced pressure. The solution
was filtered, and the remainder of solvent v/as evaporated
(the last trace of dicyclopentadiene being removed under
hard vacuum) . The cyclopentadiene adduct 4_3 was isolated by
preparative layer chromatography (pentane, 3 elutions) side-
by-side with authentic material on the sar,\o plate. An
ultraviolet spectrum in iso-octane established the presence
of 4_3 (0.0031 g, 0.012 mmol , 4.7% yield).
b) In an identical experiment, 1 , 3-cyclopentadiene
was added 125 seconds after photolysis ceased. An equiva-
lent workup and quantitative determination by uv spectro-
photometry indicated the formation of adduct A3_ (0.0024 g,
0.0094 mmol, 3.6% yield).
Generation of Dibenzo [a, e] cycloheptatrienylidene (32)
in the Presence of Furan.--a) 5/j'-Dibenzo [a^ c] cyclohepten-5-one
tosylhydrazone sodium salt (£1') (0.15 g, 0.38 mmol) v;as
photolyzed 30 minutes at -60 in a 1:1 by volume solution
of dry tetrahydrofuran and furan (freshly distilled from
sodium hydroxide) of total volume 25 ml. The reaction
mixture was allowed to come to room temperature and filtered.
Solvent was removed, and the remaining yellow oil was sepa-
rated by preparative layer chromatography (benzene, 2 elu-
tions) . The major product, 1 ,7- (o-biphenylenyl) -enao-2 , 5-
92
epoxynorcar-3-ene (£4) (0.046 g, 0.18 mmol, 47% yield), was
the fourth distinguishable band (just preceding a pale
yellow material) on the preparative plate and quenched uv
light rather poorly. Recrystallization from benzene-hexane
and then from 95% ethanol gave white needles with the
following properties: mp 157-158°; uv: A (CHaCN) , 307 nm
(c 3,400), 268 (sh, 14,300), 234 (30,600); ir (KBr) : 3060,
3030, 1490, 1450, 1435, 1045, 1000, 970, 760, 745, 730, 620
575 cm"-'-; "'■H-nmr (CDCI3): i 1.9-2.15 (m, 2H) , 2.4-3.0 (m,
711), 3.35-3.55 (d of doublets, IH) , 4.98 (d of doublets, 2H) ,
6.39 (d, Jg ^=2.6 Hz, IH) , 9.60 (d, J^ ^=2.6 Hz, IH) ; Table
7 lists H-nmr (CDCI3) as a function of mole ratio of Eu(fod)3
added (nonaromatic protons only, 0.035 g 4_4 in 0.5 ml CDClsf
see, also, Figure 7):
Table 7
Effect of Added Shift Reagent on H-nmr Spectra of Adduct 44_
Mole ratio Hz Downfield from TMS at 100.1 MHz
Eu(fod)3:44 h2 H3 H4 H5 H6 H7
0.0
506
707
652
499
40
361
0.2
1197
954
914
1187
349
1149
0.4
1739
1153
1118
1674
582
1760
0.6
2180
1322
1286
1980
744
2220
mass spectrum: m/e 258 (M ) (low temperature required or the
M peak disappears and one at 380 appears) .
Anal. Calcd. for CigHmO: C, 88.34; H, 5.46. Found:
C, 88.27; H, 5.51.
93
b) Room teiiiperature photolysis of 5/y-dibenzo [a, c] cyclo-
hepten-5-one tosylhydi-azone sodium salt (4j^' ) (0.143 g, 0.36
mraol) in a 1:1 by vol unc tetrahydrof uran-f uran solution (40
ml) for 15 minutes with other conditions and workup identical
to those employed in tlie lov/ temperature photolysis experi-
ment yielded adduct £4 (0.04 0 g, 0.15 mmol, 43% yield) as
the major product. Physical and spectral properties were as
reported for the material formed on low temperature photolysis
c) Room temperature photolysis of 5/i'-dibenzo [a^ c] cyclo-
hepten-5-one tosylhydrazone sodium salt (41^') (0.117 g, 0.30
mmol) in 25 ml 1:1 by volume tetrahydrof uran-f uran for 50
minutes with conditions and workup identical to those of
0^) above gave 1 , 7- (ij-biphenylenyl) -cndo- 2 ,5-epoxynorcar-3-ene
(£4) .(0.004 g, 0.015 r.jv.ol, 5% yield) as a minor product.
d) Pyrolysis of 5/7-dibenzo [a, c] cyclohepten-5-one
tosylhydrazone sodium salt (^' ) (0.10 g, 0.25 mmol) was
carried out at 115° in 15 ml furan for 30 minutes. The
reaction mixture v/as cooled and suction filtered. Furan was
evaporated. Adduct 4£ (0.0072 g, 0.028 mmol, 11% yield) was
isolated by preparative layer chromatography (benzene, 2
elutions) as a minor product and was identical by tic, uv,
and H-nmr to material previously obtained. There was no
indication of any exo-cpoxy isomer.
Photolysis of 1 , 7- (o-Biphenylenyl) -e^KJo- 2 , 5-epoxynor-
^^^~3-ene (44) .--1 , 7- (c;-Biphenylenyl) -encfo- 2 , 5-epoxynorcar-
3-ene (44_) (0.025 g, 0.10 mir.ol) was photolyzed 1 hour in
30 ml dry tetrahydrof uran. Adduct £4 was completely destroyed
94
(<5% remaining) . Three products resulted and were separated
by preparative layer chromatography (benzene) . Two of these
components had the blue fluorescence under uv irradiation
commonly associated with substituted phenanthrenes . The
major product (R^=0.2, blue fluorescence, 0.013 g) had an
nmr that implies a phenanthro [ Z ] cycloheptatrien-1-ol struc-
ture: ^H-nmr {CDCI3): t 1.2-1.6 {m, 211), 1.85-2.6 (m, 6H) ,
3.3 (ca. d, IH) , 3.8 (bs , 2IJ) , 4.7 (ca. d, IH) , 6.5 (d, Hi),
7.15 (s, IH) . The other tv;o compounds were isolated in only
minor amounts: R,=0.8, blue fluorescence, 0.003 g; Rj=0.6,
0.003 g.
Pyrolysis of 1 ,7- (c-Biphenylenyl) -encio-2 ,5-epoxynor-
car-3-ene (4_4) in Benzene. — 1 , 7- (a-Biphenylenyl) -cndo-2 , 5-
epoxynorcar-3-ene (1.194 x 10 ' g, 4. 03 x 10 mmol) was
dissolved in 5 ml benzene (spoctrograde) and heated at
12515° under nitrogen in a sealed tube for 2 hours. Tic
{pentane/5% benzene) showed complete destruction of starting
material and formation of a single new product with R^ about
twice that of starting material 44^. The new product was not
9- (2 ,4 ,6-cycloheptatrien-l-yl) -phenanthrene (42^) as shown
by a tic comparison with a previously characterized sample
of this compound although it had a similar blue fluorescence
under uv light. Nmr (microtube) suggested that this
pyrolysis product was a substituted phenanthrene (t 1.1-1.4
(m, 211) and 2.1-2.9 (m, 611)).
95
Pyrolysis of 5g-Dibenzo [g, g] cyclohepten-5-one Tosyl-
hydrazone Sodium Salt (41^') in the Presence of 2,3,4,5-
Tetraphenylcyclopentadienone . — 5//-Dibenzo [a^o] cyclohepten-
5-one sodium salt (4J^' ) (0.32 g, 0.80 mraol) and 2,3,4,5-
tetraphenylcyclopentadienone (1.00 g, 2.6 mmol) v/ere dis-
solved in 15 ml dry tetrahydrofuran and stirred rapidly at
110+5 for 3.5 hours in a 3 oz Fisher-Porter Aerosol Compati-
bility Tube. The tube was cooled to room temperature,
propiolic acid (1.09 g, 15.6 mmol) added, and the mixture
reheated in the sealed tube at 110+5 for 80 minutes and then
cooled and diluted with 50 ml toluene. Sodium carbonate was
added. The mixture was stirred 4 hours and filtered. Solvent
was removed, and preparative layer chromatography (cyclo-
hexane-benzene, 2:1, 3 elutions) permitted isolation of the
principal product as the only major band that moved up the
plate (fastest moving band, intense blue fluorescence under
uv light). The product, 10 , 11 , 12 , 13-tetraphenyl-9//-cyclo-
hepta [I] phenanthrene (4_6) (0.218 g, 0.40 mmol, 50% yield),
crystallized as a white powder contaminated with a trace of
9 ,10 , 11,12-tetraphenyl-llff-cyclohepta [Z] phenanthrcne (47)
or perhaps 9 ,10 , ll,12-tetraphenyl-9ff-cyclohepta [Z] phenanthrene
(47' ) [■'"H-nmr (CDCI3): t 4.52 (bs, methine,H)]. Recrystalli-
zation from benzene-pentane gave pure 4 6 (0.167 g, 0.31 mmol,
38% yield) with the following properties: mp 214-215 ; uv:
X^^^(CH3CN), 357 nm (e 1,300), 338 (sh, 3,200), 272 (sh,
42,000), 257 (60,000); ir (KBr) : 3080, 3060, 3020, 1600,
1490, 1440, 1075, 1020, 910, 755, 720, 700 cm""""; ''"H-nmr
96
(CDCli): T 1.25-1.6 (m, 2H) , 1.85-2.25 (m, 2H) , 2.4-2.9 (m,
411), 3.09 (bs, 2011), 5.38 (d, J=12.5 Hz, 111), 6.08 (d ,
J=12.5 Hz, 111); mass spectrum: m/e 546 (M , 100), 469 (17),
455 (13), 392 (26), 369 (45), 292 (14), 290 (19).
Anal. Calcd. for C43H3o: C, 94.47; 11, 5.53. Found:
C, 94.27; fl, 5.67.
Thermal RearrangGmont of 10 , 11 , 12 , 13-TetraphGnyl-9//-
cyclohepta [Ijphenanthrene (4[6) . — a) 10 ,11, 12 , 13-Tetraphenyl-
9W-cyclohepta [l]phenanthrene (46^) (0.07 g, 0.13 mmol) was
dissolved in 0.5 ml tetrachloroethylene and placed in an
nmr tube. Nmr spectra were taken as the temperature was
gradually increased. No change in the spectrum occurred
until the temperature reached 150 . Heating at 160 for
1 hour caused the doublet of doublets (x 5.38 and 6.08,
J=12.5 Hz) to lose resolution and broad humps to appear in
the same region of the spectrum. On cooling tlie nmr spectrum
showed the doublets due to 4^ along with the broad singlet
(t 4.52) due to an H-shift isomer 4_7^ or 4_7_' and totally
aromatic material. Preparative layer chromatography (cyclo-
hexane-benzene , 2:1, 3 elutions) failed to separate the
components. Recrystallization from chloroform also failed
to give a pure product. The mass spectrum of the mixture
had a parent ion at 546 of more than 5 times the intensity
of any other fragment, and a mp 297-299 was recorded.
b) Refluxing 4_6 in xylene 5 hours produced a mixture
with an nmr spectrum similar to that obtained after heating
97
in the nmr probe above. Heating in xylene at reflux for an
additional 5 hours reduced the amount of 46_ and 47_ slightly
relative to the totally aromatic material.
Low Temperature Photolysis of 4 , 5-Benzotropone Tosyl-
hydrazone Sodium Salt (^' ) in the Presence of 1,3-Cyclo-
pentadiene. — 4 , 5-Benzotropone tosylhydrazone sodium salt
(53') (0.256 g, 0.74 mmol) was photolyzed 75 minutes at
-60° in 20 ml dry tetrahydrofuran containing 1 , 3-cyclopenta-
8 3 o
diene monomer (7 ml, 100 mmol, transferred at -78 ).
The reaction mixture was allowed to warm to 5 , and solvent
and cyclopentadiene were removed under reduced pressure.
The residue was taken up in cyclohexane and passed through
an alumina column (Grade III) to remove sodium toluene-
sulfinate and a very slightly soluble red material that
seemed to be the major product. Solvent removal left the
hydrocarbon products (0.038 g) , mainly endo-5 ,6-benzotetra-
cyclo [7 . 2 . 1. 0^ '^ . 0^ ' ^]dodeca-3 , 5 , 10-triene (£8) and a number
of minor components that appeared (nmr) to be secondary
photolysis products and naphthylcarbene addition and inser-
tion products. Preparative layer chromatography (pentane,
3 elutions, the leading band isolated) followed by molecular
distillation (90°, 0.15 mm of Hg) gave a colorless liquid
(0.025 g, 0.12 mmol, 16% yield) with the following proper-
ties: ir (film): 3060, 3020, 2970, 2930, 2860, 1485, 1455,
1330, 1235, 1040, 1025, 1000, 895, 860, 840, 785, 770, 755,
740, 730, 625 cm""""; """H-nmr (CDCI3): x 2.65-2.95 (m, 4H) ,
98
3.71 (narrow AB pattern, 2H) , 3.9-4.25 (ra, 2Ii) , C.93 (bs,
IH) , 7.05 {bs, IH) , 7.52 (d, J^ ^=2.8 Hz, IH) , 7.75-8.0
(m, J =6.8 Hz, IH) , 8.18 (d, J„^ -6.8 Hz, IH) , 9.65
' gem gem
(narrow d of doublets, J^ s"^'^ "^' "^8 9^^'^ "''^ ' "^"^ ' "^^^^
spectrum: m/e 206 (m"^ , 100), 178 (54), 165 (69); exact
mass 206.1091 (calcd. for CieHm, 206.1095).
2 7 2 8
Pyrolysis of en(io-5 ,6-Benzotctracyclo [7 . 2 . 1. 0 ' .0 ' ]-
dodcca-3,5,10-triene (4£) • — Attempted preparative gas chroma-
? 7 2 8
tography of encfo-S ,6-benzotetracyclo [7 . 2 . 1 . 0 ' ,0 ' ]dodeca-
3,5,10-triene (4_8) at 160° (18' x 1/4", 20% SE-30) gave a
single compound with tic (pentane) and nmr spectrum different
from the initially injected sample of 4_8. The nmr spectrum
is consistent with a structure such as 7 , 10-methano-ll//-
naphthola]cycloheptene: H-nmr (CDCI3): t 2.05-3.0 im, 6H) ,
3.6-3.8 (d of doublets, IH) , 4.1-4.3 (d of doublets, IH) ,
6.5-6.7 (m, IH) , 6.8-7.4 (m, 3H) , 7.6-8.1 (m, 3H) . This
material is also present as a minor product formed in the
preparation of 4_8 and is distinguishable in the nmr spectrum
of the mixture of crude hydrocarbon products. No attempt
was made to purify and characterize this material.
Low Temperature Photolysis of 3 , 4-Benzotropone Tosyl-
hydrazone Sodium Salt (53.') in the Presence of 1,3-Buta-
diene. — 4 , 5-Benzotropone tosylhydrazone sodium salt (53 ' )
(0.228 g, 0.66 mmol) in 15 ml dry tetrahydrof uran was cooled
to -60° in the photolysis cell. An equal volume of 1,3-
butadiene was condensed into the cell, and photolysis was
9 9
carried out for 2 hours. The reaction mixture was warmed
to room temperature under a stream of nitrogen as the buta-
diene evaporated. The solution was further reduced in
volume at 25° under reduced pressure and filtered through
magnesium sulfate (anhydrous) to remove sodium toluenesul-
finate and an amorphous red solid that precipitated. Prepa-
rative layer chromatography (pentane, 3 elutions) permitted
the isolation of two Cis isomers. The leading component,
4,5-benzotricyclo[5.4.0.0-'-"^]undeca-2,4,9-triene (£9) (0.014 g,
0.072 mmol, 11% yield), was obtained after molecular distil-
lation (70°, 0.15 mm of Hg) as a colorless liquid with the
following properties: uv: A (iso-octane) , 308 nm (sh,
e 1,600), 276 (6,050), 223 (22,000); ir (film): 3020, 2890,
2830, 1485, 1455, 1435, 1220, 1115, 1055, 980, 795, 780,
765, 750, 725, 670, 645 cm"-""; "'■H-nmr (CDCI3): x 2.6-3.0
(m, 4n) , 3.84 (AB pattern, 2H) , 4.35-4.55 (m, 2H) , 7.47
(bs, 411), 7.64 (d, Jg ^ = 4.7 Hz, IH) , 9.45-9.75 (m, IH) ;
mass spectrum: m/e 194 (m"^, 22), 179 (27), 141 (89),
140 (100), 124 (34); exact mass 194.108 (calcd. for CisHm,
194.1095).
Anal. Calcd. for CisHm: C, 92.74; H, 7.26. Found:
C, 92.64; H, 7.28.
The trailing component was highly contaminated with impuri-
ties, but an additional preparative layer chromatography
(pentane, 5 elutions) permitted isolation of l-vinyl-6,7-
benzospiro[2.6]nona-4,6,8-triene (5£) (0.003 g, 0.016 mmol,
3% yield) by judicious removal of the center portion of a
100
broad band of poorly separated compounds. After molecular
distillation (70°, 0.15 mm of Ilg) this spiro-compound 50^
had the following propertiuc : ir (film): 3060, 3020, 1630,
1490, 1440, 1155, 1040, 990, 940, 900, 810, 760, 745, 705 cm" ;
•^H-nmr (CDCI3): t 2.96 (s, 4H) , 3.72 (d, J4^3=11.5 Hz, IH) ,
3.84 (d, Jo 0=11.5 llz, IH) , 4.2-4.8 (m, IH) , 4.75-5.2 (m,
311), 8.25-9.2 (m, 3H) ; mass spectrum: m/e 194 (M , 73),
179 (100), 178 (62), 165 (45), 128 (96); exact mass 194.1085
(calcd. forCisHm, 194.1095).
Low Temperature Photolysis of l-Vinyl-6 ,7-benzospiro-
[2.6]nona-4 ,6 ,8-trienG (50). — In the small volume photolysis
cell (Pyrex) employing the standard conditions for low temper-
ature formation of aromatic carbenes from tosylhydrazone
salts, l-vinyl-6,7-benzospiro [2.6]nona-4,6,8-triene (50)
(0.002 g, 0.01 mmol) was photolyzed 1 hour at -60 in 20 ml
dry tetrahydrofuran. Solvent removal followed by prepara-
tive layer chromatography (pentane/5% benzene) gave approxi-
mately 75% recovery of starting material 5£ along with trace ■
amounts of two other materials neither of which waso 4,5-
benzotricyclo [5.4.0.0-'-'^]undeca-2,4,9-triene (£9) as deter-
mined by tic and uv . No trace of 4_9 could be detected by
uv spectrophotometry when that portion of the preparative
layer chromatography plate expected to contain this compound
(chromatographed side-by-side with an authentic sample of
49 on the same plate) was extracted. The limit of detection
by uv was better than 2. x 10 g (1%).
101
Pyrolysis o£ 4 ^5-Benzotropone Tosylhydrazone Sodium
Salt (52' ) in the Presence of 2 , 3 , 4 , 5-Tetraphenylcyclopenta-
dienone. — 4 , 5-Benzotropone tosylhydrazone sodium salt (53' )
(0.36 g, 1.05 mmol) and 2 , 3 , 4 , 5-tetraphenylcyclopentadienone
(1.0 g, 2.6 mmol) were dissolved in 15 ml dry tetrahydrofuran
and stirred rapidly at 115+5° for 2 hours in a sealed tube
under nitrogen. Solvent was removed under reduced pressure,
and the reaction products dissolved in 50 ml toluene. Pro-
piolic acid (1.0 g, 14 mmol) was added, and the solution
heated at reflux 30 minutes (until the tetracyclone color
lightened) . The solution was cooled, and an excess of
sodium carbonate added. After stirring 30 minutes, the
mixture was filtered through Celite 545. Solvent was
removed under reduced pressure, and the residue twice sub-
jected to preparative layer chromatography (benzene-carbon
tetrachloride-pentane, 1;1:1, 3 elutions) . Three products
were obtained. 7 , 8 ,9 , 10-Tetraphenyl-9^-cyclohepta [a] naphtha-
lene (5^) (0.046 g, 0.093 mmol, 9% yield) was the fastest
moving component and had a bright blue fluorescence under
uv light. It was recrystallized from benzene-pentane as a
colorless solid with the following properties: mp 212-213 ;
uv: X (CH3CN), 330 nm (sh, e 13,000), 281 (39,500), 240
in 3.x
(41,000); ir (KBr) : 3060, 3010, 2920, 1600, 1495, 1445,
1080, 1035, 820, 770, 700, 600, 550, 530 cm""*"; H-nmr (CDCI3)
T 1.6-1.9 (m, IH) , 2.21 (bs , IH) , 2.3-3.3 (m, 25H) , 4.57
(bs, IH) ; mass spectrum: m/e 496 (m"^ , 100), 419 (17), 406
(10) , 342 (59); exact mass 496.2143 (calcd. for C39H28/
102
496.219.1). The second component on the plate (0.160 g,
0.305 iTimol, 29% yield) was tentatively identified as 6a, 11a-
dihydro-7 , ft , 9 , ] 0- tctraphenylbenzo [a] naphtho [2, 1-ci] furan (56)
from the following spectral properties of 5£ after a recrys-
. tallization from benzene-pentane : mp 275-277 ; uv:
X ,(CH3CN), 300 nm (e 6,800), 243 (45,000); ir (KBr) : 3060,
3030, 2910, 1600, 1565, 1495, 1445, 1400, 1295, 1210, 116C,
1075, 1030, 940, 915, 830, 795, 755, 700, 660, 600, 560,
545 ci.r-'-; Hi-nnr (CDCI3): T 2.5-3.0 (m, 9H) , 3.20 (bs, 15H) ,
3.69 (d of doublets, J^ ,--9 Hz, J^ , =2.5 Hz, IH) , 4.24
b , D D , ba
(d, J, -,-, =^9 Hz, IH) , 4.76 (d of doublets, J^ ^ = 9 Hz,
t) 1 1 , 1 1 a -> , b
J^ , =3 Hz, in), 5.58 (d of triplets, J, n =9 Hz,
o , ba ba , 11a
.+
Jc , =J, ^ =2.5-3. Hz, in); mass spectrum: m/e 524 (M ).
D,ba b,ba
Anal. Calcd. for C<,oH260: C, 91.57; H, 5.38. Found:
C, 91.25; H, 5.40.
The third product with the smallest R, value was 6-naphthyl-
tetraphenylphenol (55^) (0.094 g, 0.18 mmol> 17% yield). The
optimum yic-ld of 5^ may not have been obtained since workup
conditions could have removed a portion of this product.
The crude material became bright orange in the presence of
sodium hydroxide and an nmr signal at x 4.78 was removed by
shaking with deuterium oxide. Recrystallization from
ethanol-water gave pure 5_5 with the following properties:
mp 235-237°; ir (KBr): 3530, 3050, 3020, 1600, 1500, 1440,
1400, 1290, 1270, 1200, 1135, 1105, 1070, 750, 725, 700,
600, 480 cm""^; """H-nmr (CDCI3): t 2.2-2.9 (m, 12H) , 3.2 (d,
15H) , 4.78 (s, IH) ; mass spectrum: m/e 524 (m"*") .
103
Anal. Calcd. for C^oUstO: C, 91.57; H, 5.38. Found:
C, 91.39; H, 5.42.
Thermolysis of 5_4, 55^, anvl 56 each in a separate sealed
tube at 115+5° in tetrahydrofuran for 2 hours failed to
convert any compound to any other. All were stable to the
thermolysis conditions as determined by tic (benzene) .
55 and 56^ were also stable to p-toluenesulfonic acid treat-
ment in acetonitrile at room temperature for 24 hours as
determined by tic (benzene) .
Pyrolysis of Tropone Tosylhydrazone Sodium Salt in
Furan . --Tropone tosylhydrazone sodium salt (0.50 g, 1.7
mmol) in 30 ml furan was heated at 12013 for 2 hours in a
sealed tube. The dark reaction mixture was cooled to room
temperature and filtered. The solvent volume was reduced to
a convenient size for transfer to a preparative layer chroma-
tography plate. Chromatography (pentane-ether-benzene,
5:3:2, 2 elutions) gave «72;c- 1 , 4-epoxy-4a//-benzocycloheptene
(57) (0.155 g, 0.98 mmol, 58% yield) as the major product
along with heptaf ulvalene . The R^ of 57_ was about twice
that of heptaf ulvalene. Nmr spectra of the minor components
gave no indication of the cfido-epoxy isomer. Adduct 57^
solidified on vacuum transfer and had the following proper-
ties: mp 47-48.5°; uv : A (CH3CN), 304 nm (e 1,700), 201
(18,000); ir (melt): 3020, 2860, 1315, 1290, 1055, 1030,
1000, 900, 860, 850, 825, 785, 765, 725, 705, 695, 630 cm"-'-;
•'"H-nmr (CDCI3): t 3.17 (d of doublets, J^ ^ = 2 Hz, J^ ^=6 Hz,
104
111), 3.71 (d of doublets, 3^ 3=6 Hz, J^ 4 = ^-"^ "2' ■'''^'
3.8-4.4 {m, 411), 4.63 (bd, J^ 4a"'''^ "^' ^"^ ' ^'^^ ^^^' "'■"^ '
5.54 (d of doublets, J^ 5=^*^ ^'^' "^5 6^^ "^'' ■'"^' ^•'^^"^•^^
(m, IH) ; Table 8 lists -^n-nmr (CCIm) as a function of mole
ratio of Eu(fod)3 added (0.060 g 57 in 0.5 ml CClu, see,
also, Figure 10) :
Table 8
Effect of Added Shift Reagent on H-nmr Spectra of Adduct 52
Mole ratio Hz Downfield from TMS at 100.1 MHz
Eu(fod)3:57 Hi H2 H3 H4 Il4a H5 h6,7,8 H9
0.0 487 675 619 525 337 436 590 610
0.2 1144 945 888 1150 749 661 705 775
0.4 1550 1104 1042 1557 1025 741 723 843
mass spectrum: m/e 158 (m"^, 74), 129 (100), 128 (98), 105
(61) .
Anal. Calcd. for CiiHioO: C, 83.52; H, 6.37. Found:
C, 83.38; H, 6.43.
Generation of Phenanthrylcarbene (3^) in the Presence
of Furan.--a) Phenanthrene-9-carboxaldehyde tosylhydrazone
sodium salt (4_5 ' ) (0.25 g, 0.63 mmol) was photolyzed 1.5
hours at -60 in a 1:1 by volume solution of tetrahydro-
furan-furan of total volume 30 ml. The reaction mixture
was allowed to come to room temperature and filtered. Sol-
vent was removed, and the residue was inspected by H-nmr
spectroscopy. There was no indication of the formation of
any 1 ,7- (o-biphenylenyl) endo-2 , 5-epoxynorcar-3-ene (44).
105
Preparative layer chromatography (benzene, 2 elutions)
side-by-side with authentic 4i_ on the same plate, extraction
of the portion of the plate expected to contain 4_4, and
analysis by uv spectrophotometry failed to indicate the
presence of adduct 44_ to a limit of detection of better than
2. X 10~^ g (0.1% yield) .
b) Phenanthrene-9-carboxaldehyde tosylhydrazone sodium
salt (4_5 ' ) (0.50 g, 1.26 mmol) was pyrolyzed in 20 ml neat
furan (sealed tube) for 1 hour at 115±5 with rapid stirring.
The reaction mixture was cooled to room temperature and fil-
tered. Solvent was removed. No trace of adduct £4_ could
be detected in the H-nmr spectrum of the residue or by tic
(benzene) . The H-nmr and tic of the product mixture were
remarkably different from those of the product mixture from
pyrolysis of 5i/-dibenzo [a^ c] cyclohepten-5-one tosylhydrazone
sodium salt (41^') under similar conditions.
c) Phenanthrene-9-carboxaldehyde tosylhydrazone sodium
salt (4_5 ' ) (2.5 g, 6.3 mmol) was placed in a sublimer and
heated at 120 overnight (10 mm of Hg) . Impure phenan-
thryldiazomethane (0.24 g, major contaminant apparently
46
phenanthro [9 ,10-(3]pyrazole ) collected on the sublimer
cold finger. The diazo-compound was dissolved in 20 ml of
a 1:1 by volume solution of tetrahydrof uran-f uran and
photolyzed at room temperature for 20 minutes. Solvent was
removed. No trace of adduct 4_4 was indicated by nmr or tic
(benzene) of the residue.
106
Low Temperature Photolysis of the Sodium Salt oi: 5/7-
Dibenzo [a, clcyclohepten-5-one Tosylhydrazone (41^') in the
Presence of Diethylamine.--a) 5//-Dibenzo [a, c] cyclohepten-
5-one tosylhydrazone sodium salt (41^') (0.20 g, 0.50 mniol)
and diethylamine (2.50 g, 34. mmol , distilled from LAII) were
mixed in 20 ml dry tetrahydrofuran. The solution was photol-
yzed 45 minutes at -60°. The reaction mixture was warmed
to room temperature, and the sodium toluenesulf inate
dihydrate^^ (0.074 g, 0.35 mmol, 69% yield) was filtered off.
Solvents were removed, and the H-nmr spectrum of the residue
gave no indication of the presence of a diethylamine addi-
tion product (no ethyl signal) . Both nmr and tic of the
product mixture were similar to those of reaction mixtures
from photolysis of £1' in the absence of trapping reagents
or in the presence of ineffective traps such as styrene or
dimethyl f umarate .
b) A similar H-nmr spectrum resulted when a like
quantity of the salt 4_1' was photolyzed in neat diethyl-
amine at -30 + 10*^ with other conditions and wor)cup similar.
There was no indication of an amine adduct.
Photolysis of Phenyl Azide in the Presence of Butyl-
90
amine. — a) Phenyl azide (2.08 g, 17.5 mmol) was photolyzed
1 hour at room temperature in dry tetrahydrofuran containing
butylamine (21. g, 290 mmol, distilled from LAH) . An Hanovia
preparative scale photolytic reactor (Pyrex, total volume
250 ml) was used and a nitrogen atmosphere maintained. Sol-
107
vent and unreacted amine were removed under reduced pressure,
and the inajor product, 2-N-butylamino-3//-azepine (61b) , was
vacuum distilled lO.l -..u.^. of Hg, 92-105°) from the dark
residue. The product Clb (2.09 g, 12.7 mmol, 73% yield)
72*^ 9 ^
had the anticipated "^ ' '■ spectral properties: ir (film):
3240, 3040, 2960, 2930, 2870, 1580, 1525, 1425, 1365, 1250,
1210, 1170, 880, 780, 740, 690 cm"-""; ^H-nmr (CDCI3): x 2.95
(d, IH) , 3.80 (d of doublets, IH) , 4.28 (d of doublets, IH) ,
4.85 (d of doub]ots, l.'i) , 5.54 (bs , IH) , 6.75 (ca. t, 211),
7.40 (d, 211), 8.3-8.85 (m, 4II) , 8.9-9.3 (m, 3H) .
b) Preparative scale photolysis of phenyl azide^°
(2.00 g, 16.8 mmol) in 250 ml dry tetrahydrof uran containing
one equivalent of butylamine (1.23 g, 16.8 mjnol, distilled
from LAH) was carried out at room temperature under nitrogen
with a 550 W Hanovia lamp in an Hanovia immersion well (Pyrex,
water cooled). After photolyzing 1 hour, solvent was removed
and the dark residue vacuum distilled (0.25 mm of Hg,
96-106°). 2-N-}3Utylamino-3/.'-azepine (6^b) (1.85 g, 11.3
mmol, 67% yield) was thus obtained as a pale yellow oil
with spectral properties (ir, H-nmr) as previously
91
reported and identical with the major product 61b iso-
lated from reaction in the presence of excess amine (see (a)
above) .
c) Under identical conditions to those employed in the
previous experiment (see(b) above) but with furan (250 ml)
rather than tetrahydrof uran as solvent, phenyl azide^^
(2.00 g, 16.8 mmol) v/as photolyzed in the presence of one
108
equivalent of butylamir.e (1.23 g, jC.a ii.iicx) r^r 1 hour at
room temperature. After vacuum distillcition (0.2 mm of Ilg,
95-106°), 2-N-butylamino-3//-a7:fipino (Gib) (1.8') g, 11.3 mmol ,
67% yield) was isolated with physical and spectral proper-
ties identical to the product obtained v;hen tetrahydrof uran
was used as solvent (see (b) above) .
Photolysis of Phenyl Azide in the Presence of Furan. —
Under preparative photolysis conditions at room temperature,
phenyl azide^^ (0.513 g, 4.3 mmol) and furan (20 g, 290 mmol)
were dissolved in approximately 250 ml dry tetrahydrof uran.
Photolysis was carried out under nitrogen with rapid stirring
for 5.2 hours with water cooling (550 W Ilanovia lamp). Sol-
vent was removed from the opaque red-black reaction mixture,
and CDCI3 added to the residue. The polymeric products were
too viscous to pass through a fritted filter funnel, and the
H-nmr spectrum showed only broad humps in the aromatic
region along with some unreacted phenyl azide. Tic (benzene)
streaked badly, and only the colored spot due to phenyl
azide was distinguishable. The reaction mixture is apparently
similar to that which results from photolysis of phenyl
74
azide in neat tetrahydrof uran .
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112
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113
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114
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BIOGRAPHICAL SKETCH
Thomas Tyler Coburn was born May 8, 194 3, in Montebello,
California^ and attended Whittier Union High School in
VJhittier, California. He received the B.S. degree from
Harvey Mudd College in Claremont, California, June, 19G5,
and the M.S. degree from Yale University in January, 1967.
He worked briefly as a development chemist at Geigy
Chemical Corporation in Cranston, Rhode Island. From
September, 1967 until June, 1970, he was Instructor and then
Assistant Professor of Chemistry at Mount Saint Mary College
in Nev;burgh, New York.
In June, 197 0, he began graduate work toward the degree
of Doctor of Philosophy at the University of Florida.
During graduate study he held a National Science Foundation
Science Faculty Fellowship (1971-1972) and a University of
Florida Graduate Council Fellowship (1972-1973) .
Mr. Coburn is married to the former Susan Fones Dunn
of Wethersf ield, Connecticut. He is the father of Matthew
Tyler and Katherine Louisa and is anticipating an additional
member of the family in October, 1973.
115
I certify that I have read this study and that in my
opinion it conforms to acceptable standards of scholarly
presentation and is fully adequate, in scope and quality
as a dissertation for the degree of Doctor of Philosophy.
V^V>.c^^
William M. Jones ,vX^airman
Professor of Chemistry
I certify that I have read this study and that in my
opinion it conforms to acceptable standards of scholarly
presentation and is fully adequate, in scope and quality
as a dissertation for the degree of Doctor .of Philosophy.
^l//Ui un ^^ 6WY^ Y.
William R. Dolbier, Jr. /
Associate Professor of Chemistry
I certify that I have read this study and that in my
opinion it conforms to acceptable standards of scholarly
presentation and is fully adequate, in scope and quality
as a dissertation for the degree of Doctor of Philosophy.
Merle A. Battiste
^
Professor of Chemistry
I certify that I have read this study and that in my
opinion it conforms to acceptable standards of scholarly
presentation and is fully adequate, in scope and quality
as a dissertation for the degree of Doctor of Philosophy.
;rt C. Stouf<
Associate Professor of Chemistry
I certify that I have read this study and that in my
opinion it conforms to acceptable standards of scholarly
presentation and is fully adequate, in scope and quality,
as a dissertation for the degree of Doctor of Philosophy.
W>(Uv Vl^v^o^ \f
0, yv^*::.
Arun K. Varma
Associate Professor of Mathematics
This dissertation was submitted to the Department of
Chemistry in the College of Arts and Sciences and to the
Graduate Council, and was accepted as partial fulfillment
of the requirements for the degree of Doctor of Philosophy,
August, 1973
Dean, Graduate School
a/
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