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Formation of Phenanthrenequinone from Benzil A Novel Reaction of Graphite-Potassium Intercalates.

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also expected to be photoactive in the far UV region since
they possess appreciable absorption below 200 nm ( o * t o
and Rydberg excitations)[21. Cyclobutane rings can be
cleaved efficiently by photochemical electron transfer with
quinones as electron acceptor^'^]. This photo-cleavage,
which involves radical cation intermediates, plays a central
role for the dissociation of thymine dimers in photodamaged DNA by photo-repairing enzymes[41.Since o*t o Rydberg excitation does lead to intermediates with radical
cation character[‘], it appeared important to explore the
possibility of promoting direct photochemical cleavage of
cyclobutanes that are devoid of chromophoric substituents
by means of 185 nm irradiation in solution. That this cleavage indeed occurs is demonstrated using bicyclo[4.2.0]octane 1 as example.
Received: April 9, 1984;
revised: June 6, 1984 [ Z 792 IE]
German version: Angew. Chem. 94 (1984) 599
Irradiation of a 0.044 M solution of 1 in n-pentane with
the full output of a mercury low-pressure lamp (Grantzel,
Karlsruhe) affords 1,7-octadiene, cyclohexene, and ethylene. These photo-products were identified by co-injecting
authentic materials onto three different capillary GC columns (86 m polypropylene glycol, 50 m OV-101, and 50 m
Carbowax 20 M). In addition, 1,7-octadiene and cyclohexene were identified by their characteristic fragmentation
patterns on capillary G U M S analysis. Finally, 1,7-octadiene was collected by preparative gas chromatography
(packed glass column 1.5 m x 8 mm, 10% P,P’-oxydipropionitrile on Chromosorb WHP, 100/200), and its 90 MHz
’H-NMR spectrum found to be identical to that of an authentic sample.
Control experiments revealed that not even traces of cyclooctene were produced in the 185 nm photolysis, and at
254nm (the major output of the mercury low-pressure
lamp) 1 was completely photo-stable. Quantitative capillary GC analysis (50 m SE 30) gave a relative product composition of 1,7-octadiene: cyclohexene = 70 :30, with a
mass balance of >98% during the first 40 min of 185 nm
irradiation. The quantum yields determined using the
(Z,E)-isomerization of cyclooctene as actin~meter[~]
Qs = 0.12 f0.01
Qp=O.lO~O.O1and @p=0.030+0.003 for 1,7-octadiene
and cyclohexene, respectively.
In comparison, vacuum flash pyrolysis of 1 (18 torr, distillation through a Quartz tube, 450°C) led to a relative
1,7-octadiene :cyclohexene = 11 :89I6I. Ethylene was also formed, but the amount
was difficult to quantify.
There are no analogous photoreactions of 1 at higher
wavelengths because this alkyl-substituted cyclob~tane[’~
has no UV absorption above 200 nm. Mercury-sensitized
irradiation of cyclooctene at 254 nm leads to 1, postulated
to be formed via cyclization of the intermediate tetramethylene diradical 1,4-~yclooctanediyl[~~.
The fact that cyclooctene is not formed in the 185 nm photolysis of 1 precludes this 1,4-diradical as reactive intermediate, at least in
its ground state. For example, in the thermolysis of the
azoalkane 7,8-diazabicyclo[4.2.2]dec-7-ene,in which a
ground state 1,4-~yclooctanediylintervenes, both 1 and cyclooctene are produced[’]. Finally, the fact that the vacuum
flash pyrolysis of 1 leads mainly to cyclohexene and ethyleneI6] is evidence against the involvement of the 1,4-cyclooctanediyl as preferred intermediate in the 185 nm photolysis of 1.
Since cyclobutane rings are efficiently cleaved in the
electron-transfer photolysis of thymine dimers with quinones via intermediary radical cations[31,we postulate that
the observed cleavage of 1 into 1,7-octadiene and cyclohexene in the 185 nm photolysis proceeds via (o,3s)-Rydberg excitation. Promotion of an electron into a 3s Rydberg molecular orbital generates a species 2 with radical
cation character“’], which on cyclobutane ring-cleavage
and electron demotion would be expected to afford the observed products. Orbital symmetry arguments[’’] also suggest that such cleavage processes should be facile. The
demonstration that cyclobutane rings can be directly
cleaved by 185 nm excitation provides novel opportunities
for mechanistic investigations.
0 Verlag Chemie GmbH, 0-6940 Weinheim, 1984
[ l ] a) R. Srinivasan, J. A. Ors, T. Baum, J. Org. Chem. 46 (1981) 1950; b) W.
Adam, T. Oppenlander, Tetrahedron Letf. 23 (1982) 5391.
[2] M. B. Robin: Higher Excited States of Polyatomic Molecules, Val. 1, Academic Press, New York 1975, p. 146.
[3] H . D. Roth, A. A. Lamola, J . Am. Chem. Soc. 94 (1972) 1013.
141 J. C. Sutherland, Photochern. Photohiol. 25 (1977) 435.
[5] W. Adam, T. Oppenlander, Photochem. Photobiol. 39 (1984) 719.
[6] J. E. Baldwin, P. W. Ford, J. Am. Chem. Soc. 91 (1969) 7192 reported cyclohexene as major product.
[7] Cyclobutanes with cbromophores can be cleaved by direct photolysis
above 200 nm, cf. E. Schaumann, R. Ketcham, Angew. Chem. 94 (1982)
231; Angew. Chem. Int. Ed. Engl. 21 (1982) 225. For the direct photochemical cleavage of a functionalized cyclobutane with radiation below
200 nm cf. M. G. Steinmetz, E. J. Stark, Y.-P. Yen, R. T. Mayes, R. Srinivasan, J . Am. Chem. Soc. 105 (1983) 7209.
[8] Y. Inoue, K. Moritsugu, S. Takamuku, H. Sakurai, J. Chem. Soc. Perkin
11 1976, 569.
191 C. J. Samuel, J. Chem. Soc. Chem. Commun. 1982, 131.
[lo] P. J. Kropp in A. Padwa: Organic Photochemistry, Vol. 4, Marcel Dekker, New York 1980, pp. 1-134.
[Ill N. L. Bauld, D. J. Bellville, R. Pabon, R. Cbelsky, G. Green, J. Am.
Chem. Soc. I05 (1983) 2378.
Formation of Phenanthrenequinone from Benzil :
A Novel Reaction of Graphite-Potassium Intercalates
By Dou Tamarkin, Daphna Benny, and
Mordecai Rabinouitz*
Reactions of the highly ordered potassium-graphite intercalate C,K have evoked recently much interest. Due to
its structure it reacts in a different mode, as compared with
non-intercalated dispersed potassium[’]. Recently, we reported that vic-dibromides undergo with C8K a stereospecific debromination reaction, and ketones undergo a bimolecular reduction in high yields to the respective pinacols.
It has been suggested that the “layer-edge mechanism” is
responsible for the specific reactivity of this reagentl2].According to this mechanism ketones which are linked to adjacent potassium atoms at the graphite layer edge, form radical anions. These radical anions can then undergo a
C-C bond formation reaction at those carbons bearing
high spin densitylZb1.
[*] Prof. Dr. M. Rabinovitz, D. Tamarkin, D. Benny
Department of Organic Chemistry, The Hebrew University of Jerusalem
Jerusalem 91 904 (Israel)
0570-0833/84/0808-0642 $ 02.50/0
Angew. Chem. lnt. Ed. Engl. 23 (1984) No. 8
2, K = CH,
4, R = CH3
We now wish to report a novel reaction that a-diketones
undergo with CsK. Benzil 1 and&-dimethylbenzil 2 with
CaK afford phenanthrenequinone 3 and 3,6-dimethylphenanthrenequinone 4, respectively. This reaction. involves an intramolecular carbon-carbon bond formation.
The products are obtained in good yields and high purity,
while experiments with dispersed potassium under similar
conditions afforded only trace amounts of the respective
quinone. Graphite-potassium intercalate C8K is formed by
heating to 200°C potassium metal and dry graphite
(B.D.H.) with magnetic stirring[31.To freshly prepared CaK
(12.5 mmol in 20 mL dry THF), 2.5 mmol of benzil 1
(0.525 g, Fluka AG in 30 mL of THF) was added and stirred at room temperature (5 h, inert atmosphere). During
this period of time hydrogen gas evolves. The red reaction
mixture was quenched carefully with water and filtered,
extracted with CHzCI, and evaporated. Phenanthrenequinone 3 (3.7 g, 70%, m.p. 208°C(EtOH)[41was obtained.
Similarly, 3,6-dimethylphenanthrenequinone 4 was prepared from p,p’-dimethylbenzil in 72% yield (m.p. 216”C/
MeOH)[41.The same reactions can also be performed in
benzene or cyclohexane and the yields are 35% and 32%,
This novel C-C bond formation reaction provides a
new synthetic pathway for the preparation of phenanthrenequinone-type compounds and their derivatives, especially in view of the easy affordability of substituted benzil
derivatives from the corresponding benzaldehydes.
The evolution of the hydrogen gas was followed and
measured. The rate of the gas evolution was found to be
constant. This observation may indicate that the process is
“layer-edge” controlled, i.e. the rate is determined by the
surface area of the graphite lattice which contains ordered
potassium atoms available for the reaction. This is consistent with the mechanism that we have previously described
for the bimolecular reduction of ketoneslZb1.The mechanistic behavior of C8K reactions with ketones, diketones and
their analogs is under further investigation.
Received: March 5, 1984 [Z 739 IE]
German version: Angew. Chem. 96 (1984) 594
[I] General reviews: (a) M. A. M. Boersma, Cat. Rev.-Sci. Eng. 10 (1974)
243: (b) A. McKillop, D. W. Young, Synthesis 1979, 401, 481; (c) R. Setton, F. Beguin, Synfhetic Metals 4 (1982) 299.
[2] a) M. Rabinovitz, D. Tamarkin, Synfhetic Commun., in press; b) D. Tamarkin, M. Rabinovitz, Synthetic Metals 9 (1984) 125.
[3] CsK was prepared in a modified procedure following the preparation of
Lallancette, see: J. M. Lallancette, G. Rollin, P. Dumas, Can. J . Chem. 50
(1972) 3058.
[4] Literature m.p. (3) 2O8-21O0C, (4) 212-213”C, from I. Heilbron: Dictionary ofOrganic Compounds, 5th ed. Chapman and Hall 1982, pp. 2197,
4570; C1 Mass Spectra and NMR Spectra (300 MHz) were identical t o
those of authentic samples.
[5] Conversion of benzil to phenanthrenequinone, catalyzed by AICI, with
low yields, was described by E. Abel, Eer. Dfsch. Chem. Ges. 55 (1922)
Acknowledgement: We thank Dr. S. Zifrin of the laboratories of the Israel Police Headquarters for CI MS measurements.
Organotransition Metal Chemistry: Applications to Organic Synthesis. By S. G. Davies. Pergamon Press, Oxford 1982. x, 411 pp., bound, $ 85.00.
The use of transition metal complexes for the formation
of carbon-carbon bonds is not in itself new; the classical
investigations of Roelen and Reppe are nearly half a century old. Since then, however, the tremendous growth of
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The author of the present monograph has aimed at acquainting the organic synthesis-oriented reader with the
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reactions are also described. Each section is provided with
a rich selection of literature examples. It is a pity that, nevertheless, such established reagents as organocopper compounds, which play such an important role in the formation of C-C bonds remain unmentioned-possibly because they are the subject of a recently published monoAngew. Chem. I n f . Ed. Engl. 23 (1984) No. 8
graph by G . Posner. In addition to established catalytic
processes, the main treatment is of stoichiometric reactions
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The same theme has been the subject of several monographs lately. Nevertheless, this book by Davies is a welcome addition. It is clearly set out according to mechanistic principles and is thus of value as a primary reference
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synthetic problems. Why this book, which is directly reproduced for the sake of topicality, is so expensive, is quite
another question.
Karl Heinz Dotz [NB 623 IE]
Anorganisch-chemisches Institut
der Technischen Universitat Munchen (FRG)
Molecular Biology of the Cell. By B. Alberts, D . Bray, J.
Lewis, M . Raff; K . Roberts, and J . D. Watson. Garland
Publishing, New York 1983. xxxix, 1142 pp., bound,
L 33.95.
This textbook, which has been written by a group of authors, deals with only one subject, the cell, from various
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graphite, potassium, reaction, intercalated, formation, phenanthrenequinone, novem, benzin
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