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Inhibition of Bond Exchange in Cyclooctatetraenes.

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Use of a microwave-generated discharge in argon/iodine[']
as radiation source (h206 nm) has made possible the
irradiation of liquid benzene specifically in the So + S,
band (A,,, 203 nm) without direct population of the S,
state. Such irradiation of liquid benzene under standardized
conditions (20°C, 90 min, 2-ml samples) led typically to
concentrations of Dewar-benzene, fulvene, and benzvalene
of 3013, 5 0 1 5 , and 150F10ppm, respectively (GLC
retention times, UV-spectrum of fulvene, half-lives of
Dewar-benzene and benzvalene). The amounts and proportions of these isomers were the same from both airsaturated and argon-saturated benzene'"'. Thus the s,
state of benzene is clearly implicated at some stage in the
formation of Dewar-benzene, but these results on their
own do not exclude the intermediacy of So, S,, or triplet
states produced from the S, state by internal conversion.
The intermediacy of the So and S, states in the formation
of Dewar-benzene i s rendered improbable by the absence
of this isomer from the products of prolonged irradiations
(e.g. 48 h) of liquid benzene in the So S, band, both at
254 nm and over the whole band. One could only reconcile
the intermediacy of So or S, states with this evidence by
the rather strained postulation of the need for some critically high vibrational levels inaccessible by direct irradiation in the So+ S, band, and, as noted above, the transformations would be symmetry forbidden. The idea of
vibrationally excited intermediates also seems at variance
with the observed need for a liquid- rather than a gasphase',].
The possible intermediacy of triplet states of benzene in
the formation of Dewar-benzene was tested by comparison
of the rate of formation of Dewar-benzene from pure
benzene with that from dilute solutions of benzene in ciscyclooctene and cyclooctane. cis-Cyclooctene acts as an
energy acceptor from T, benzene, giving the trans-isomer[61,
and other olefins are well known to behave similarly[71.In
fact, irradiation of 10% solutions of benzene in cis-cyclooctene at 206 nm as above surprisingly increased the rates
of formation of Dewar-benzene, fulvene, and benzvalene
approximately 20-fold in comparison with the rates from
pure liquid benzene under comparable conditions, and a
similar degree of insensitivity to dissolved air was observed[**''. A similar increase (22-fold) was found with the use
of cyclooctane as medium, so the dilution effect is physical
rather than chemical in nature. The greatly increased rate
of formation of Dewar-benzene in the presence of the olefin
rules out any appreciable contribution from triplet benzene
as an intermediate. Thus the evidence leaves S, benzene as
the only reasonable direct precursor of Dewar-benzene.
The question whether Dewar-benzene can also arise from
S, ('E,u) benzene was investigated by the use of an oxygen
lamp emitting over the range ca. 160-220nm'31, and a
filter of 0 . 9 % ~aqueous LiCl to isolate the So+ S, band
when necessary. It was found that Dewar-benzene can also
arise from population of the S, state: the results are consistent with direct isomerization of this state or of some
state (e.g. S , benzene) derived from it.
states to the S , state (which is normally unity for most
organic molecules that have been studied in dilute solution)
is significantly less than unity in the cases of benzene and
some methylbenzenes[']. The present results suggest that
part at least of the discrepancy can be attributed to a tendency for 1,4-bonding in the S, state of benzene.
Received: June 14,1971 [Z 474a IE]
German version: Angew. Chem. 83,803 (1971)
[l] J. M. Blair and D. Bryce-Smith, Proc. Chem. SOC.1957,287; H . J.
F. Angus, J . M . Blair, and D. Bryce-Smith, J. Chem. SOC.1960,2003.
[Z] K. E. Wilzbach, J . S. Ritscher, and L. Kaplan, J. Amer. Chem. SOC.
89, 1031 (1967); L. Kaplan and K . E . Wilzbach, ibid. 90, 3291 (1968).
[3] H . R . Ward and J . S . Wishnok, J. Amer. Chem. SOC.90,1085, 5353
[4] D. Bryce-Smith and H . C. Longuet-Higgins, Chem. Commun. 1966,
593; I . Huller, J. Chem. Phys. 47, 1117 (1967); D. Bryce-Smith, Pure
Appl. Chem. 16,47 (1968); R. Hofmann and R. B. Woodward, Accounts
Chem. Res. 1, 17 (1968).
[ 5 ] P. Harteck, R. R. Reeces, and B. A. Thompson, 2. Naturforsch. 19a,
2 (1964).
[6] B. H. Orger, Ph. D. Thesis, University of Reading 1969; cf. J. S.
Swenton, J. Org. Chem. 34, 3217 (1969).
[?I P. J. Kropp and H . J . Krauss, J. Amer. Chem. SOC.89,5199 (1967),
and references therein.
[8] D. Bryce-Smith, Chem. Comm. 1969, 806.
[9] C. L. Braun, S. Kato, and S. Lipsky, J. Chem. Phys. 39, 1645 (1963).
Inhibition of Bond Exchange in Cyclooctatetraenes
By D. Bryce-Smith, A. Gilbert, and J . Grzonka"]
The [4n]annulenes so far studied exhibit (a) bond-alternation, and (b) bond-exchange" - Previous workers have
shown that the rate of bond-exchange in the cyclooctatetraene ring tends to be decreased by mono- and 1,Z-disubstitution, and that in the latter case the equilibrium
favors the less overcrowded tautomer
We now
report NMR and chemical evidence which, taken together,
suggests that certain 1,2-disubstituted cyclooctatetraenes
exist exclusively in form A.
Dimethyl cyclooctatetraene-l,2-dicarboxylate( I ) shows
an NMR spectrum (Table) which remains unchanged over
the temperature range -40 to +20O0C, apart from minor
It is interesting that Bruurr, Kato, and Lipsky found that
the internal conversion efficiency from upper electronic
p*]The effect of the atmosphere on the process was examined for
samples irradiated for 10 min since with the argon-saturated solutions
significant amounts of an opaque polymer formed on the cell windows
when the irradiation time was greater than ca. 30 min.
[***I The same mixture of cyclooctene-benzene 1,3-adducts was formed as is produced by irradiation at 254 nm, a result which suggests that
higher excited states of benzene were not directly involved in the intermolecular cycloaddition process : cf. ref. [8].
f 4)
[*] Prof. D. Bryce-Smith, Dr. A. Gilbert, and J. Grzonka
Department of Chemistry, University of Reading
Whiteknights Park, Reading R G 6 2 A D (England)
Angew. Chem. internal. Edit. / Vol. I0 (1971) N o . 10
band shifts. The apparent lack of coupling between H,H,
and H,H, is surprising, but another example of this is
known['1. The tabulated data are inconsistent with the
It is estimated that any
presence of form B: cf.
contribution from form B greater than 2% would have
been detected. Analysis of the NMR spectrum of the
corresponding 1,2-dicarboxylic acid (2) leads to a similar
conclusion (see Table).
Table. NMR spectra of compounds ( I ) , (21, and (6) (interpreted as
in refs. 12. 3, 6, 71). The spectra are independent of temperature.
Signals (T)
2.94 (2 Hid), J = 3.0 Hz
4.02 ( 2 Hid), J = 3.0 Hz
4.09 (2H) [a]
6.33 (6H/s)
H-3, H-8, form A
H-4, H-7, form A
H-5, H-6, form A
methyl ester protons
2.88 (2 Hid)
3.5 (2 H/br. s)
2.85 ('1
2.79 (s) [b]
3.75-4.40 ( 5 Him)
6.58 (3H/s)
H-3, H-8, form A
H-4-H-7, form A
carboxylic acid protons
Received: June 14, 1971 [Z 474b IE]
German version: Angew. Chem. 83,804 (1971)
First Identification of a Steroid Carboxylic Acid in
By Woygang K . Seqert, Emilio J . Gallegos, and
Richard M . Teeter"'
may result more from steric than from electronic factors
since the NMR spectrum (Table) of ( 6 ) [ 9 1shows that it also
occurs only in form A.
(la), R = COOH
( l b ) >R = CH,
aromatic protons
+ H-3, form A
methyl ester protons
That none of form B is in fact present is also suggested by
the reported inability of the dicarboxylic acid (2) to form
a cyclic anhydride under normal conditions[*]. In contrast,
benzocyclooctatetraene-7,8-dicarboxylicacid, which must
exist solely in form (3), readily forms a stable cyclic anhydride"!
We now report that the acid (2) can be induced to form a
cyclic anhydride in low yields when treated with ethereal
dicyclohexylcarbodiimide. In contrast with the anhydride
from acid ( 3 ) , this new anhydride is highly unstable and
polymerizes rapidly. Yet fresh samples, obtained with
difficulty, showed a parent peak in the mass spectrum and
had IR and NMR spectra consistent with the presence of
vinyl protons only (z 3.7-4.45 in C,D,/(CD,),CO). Since
the properties appear to exclude the obvious structure ( 4 ) ,
we are obliged to consider the apparently more strained
structure ( 5 ) as the only one consistent with the experimental observations. The apparent failure to stabilize by isomerization to form ( 4 ) is remarkable. The strong, apparently exclusive, preference for form A in the present examples
[l] G. Schroder, J . F . M . Oth, and R. Merinyi, Angew. Chem. 77,174
(1965); Angew. Chem. inlerna~.Edit. 4, 752 (1965); G. SchrGder and J .
F . M . Oth, Tetrahedron Lett. 1966,4083; J . F . M . 0 t h and J . M . Gdles,
ibid. 1968, 6259; S . M . Johnson, I . C . Paul, and G . S. D. King, J. Chem.
SOC.B 1970,643.
[2] F. A . L. Anet and L. A. Bock, J. Amer. Cheni. SOC.PO, 7130 (1968).
[3] F . A . L. Anet, A . J . R. Bourn, and Y. S t i n , J. Amer. Chem. Sac. 86,
3576 (1964).
[4] J . F. M . Oth, R. Merinyi, Th. Martini, and G . Schroder, Tetrahedron
Lett. 1966, 3087.
[5] D. E. Gwynn, G . M . Whitesides, and J . D. Roberts, J. Amer. Chem.
SOC.87, 2862 (1965).
[6] E. Grotenstein Jr., T C. Campbeli, and T Shibata, J. Org. Chem. 34,
2418 (1969).
[7] J . A . E l k M . Y Sargent, and F . Sondheimer, J. Amer. Chem. SOC.
92,973 (1970).
[S] D. Bryce-Smith and J . E. Lodge, Proc. Chem. SOC.1961, 332; J.
Chem. Soc. 1963,695.
[9] D. Bryce-Smith, A . Gilbert, and J . Grzonka, Chem. Commun. 1970,
No. 10
R = CH,D
= CH,-O-SO,-C~H,CH,
(If), R = COOCH,(CF,),H
( l g i . R = CH,CH,COOH
(14, R
(le), R
[a] Irregular singiet
[b] Shoulder.
Angew. Chem. internat. Edit. 1 Vol. 10 (1971)
In a recent publication['], we reported forty new classes
of carboxylic acids in a Californian petroleum of Pliocene
age (10 million years old). We now wish to report the
identification of 23,24-bisnor-5a-cholanic acid ( I a) in the
same oil.
A narrow fraction of carboxylic acids (fraction D-4"',
representing 1.6% of all acids and 0.04% of the petroleum)
was converted by parallel reductions to hydrocarbons and
deuterium-labeled hydrocarbons (in the position of the
original carboxylic acid group) via the alcohols and p toluenesulfonates using LiAIH, and LiAID, in the last
step[,]. The hydrocarbon and deuteriohydrocarbon samples were then further fractionated in parallel by silica gel
and gel permeation chromatography (GPC) using previously described techniques[4! Gas chromatography (GC)
of a selected G P C fraction (100-foot by 0.02-inch ID
capillary column, coated with OV 17) in combination with
mass spectrometry (AEI MS-9) led to the identification of
compounds (1b ) and ( I c), respectively, thus showing the
acid to have structure ( l a ) .
Proof of structure was obtained by: 1. Synthesis of 23,24bisnor-5 a-cholane (1 b) by Wolff-Kishner reduction of
3-oxopregn-4-ene-20 P-carbaldehyde and subsequent catalytic hydrogenation with PtO, in acetic acid. The resulting
mixture of ( I bj and the stereoisomeric 5 p-hydrocarbon
was separable by preparative GC(6 m by 6 mm O D column,
3% OV 17 on Gas-Chrom Q) and the products distinguishable by mass spectrometry; 2. Synthesis of (1 c) by
chromic acid oxidation of 3 P-hydroxy-23,24-bisnor-5
zcholanic acid to the corresponding ketone and subsequent
Wolff-Kishner reduction to give acid ( I a ) ; the latter was
converted[41 to deuterium-labeled hydrocarbon (1c) cia
alcohol ( I d ) and p-toluenesulfonate ( I e ) with LAID,.
Mass spectral fragmentation patterns and gas chromatographic retention times of synthetic labeled ( I c) and unlabeled ( I b) hydrocarbons were identical with those obtained from the naturally occurring acid ;3. The mass spectrum of synthetic ester (1f) was identical with that obtain[*] Dr. W. K. Seifert
Chevron Oil Field Research Company, P. 0. Box 1627
Richmond, California 94 802 (USA)
Dr. E. J. Gallegos and Dr. R. M. Teeter
Chevron Research Company
Richmond, California 94802 (USA)
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exchanger, bond, inhibition, cyclooctatetraene
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