Russian Journal of Organic Chemistry, Vol. 37, No. 9, 2001, pp. 1344 1345. Translated from Zhurnal Organicheskoi Khimii, Vol. 37, No. 9, 2001,
pp. 1409 1410.
Original Russian Text Copyright
2001 by Kurbatov, Kurbatova.
SHORT
COMMUNICATIONS
Radical Anion Addition of Metal Ketyls
Derived from Benzophenone and 4-Phenylbenzophenone
to Carbon Dioxide
Yu. V. Kurbatov and A. S. Kurbatova
Alisher Navoi Samarkand State University,
Universitetskii bul’var 15/21, Samarkand, 703029 Kazakhstan
Received March 1, 2000
We have found that metal ketyls are capable of not
only participating in radical anion substitution [1, 2]
and cycloadditions reactions [3] but also adding to
carbon dioxide. The reactions of lithium and sodium
diphenylketyls and phenyl-4-biphenylylketyls I and
II with carbon dioxide in a solvating solvent (tetra-
hydrofuran) resulted in formation of the corresponding
salts of benzilic acid and hydroxy(phenyl)-4-bi-
phenylylacetic acid III and IV.
radical anion addition path. The revealed reaction
offers new possibilities for a simple synthesis of
aromatic -hydroxy acids having various groups at
the -carbon atom (e.g., acid IV) via radical anion
reductive carboxylation of ketones.
Benzilic acid (III). A suspension of 0.58 g
(25 mmol) of sodium (cut in fine pieces) in 20 ml of
anhydrous THF was added under purified nitrogen to
a solution of 4.6 g (25 mmol) of benzophenone in
30 ml of anhydrous THF. The reaction flask was
tightly capped, and the mixture was stirred on
a magnetic stirrer until the metal dissolved com-
pletely. Carbon dioxide was passed over a period of
1 h through the resulting solution of sodium diphenyl-
ketyl (Ib). The originally blue mixture turned yellow
green and warmed up. After 24, the mixture was
diluted with water and repeatedly extracted with di-
ethyl ether. The first extract was evaporated by half,
and the precipitate of benzopinacolone, mp 184 185 C
(published data [4]: mp 185 186 C), was filtered off.
The mother liquor and the other extracts were com-
bined and evaporated to obtain an oily mixture of
benzophenone and benzopinacolone, which was
treated with 1:1 pentane hexane. Benzophenone,
1.1 g (24%), was separated, and benzopinacolone was
isolated from the residue. The overall yield of benzo-
pinacolone was 2.3 g (50%). The aqueous phase was
acidified to pH 1 and extracted with benzene to isolate
benzilic acid (III). Yield 1 g (18%), mp 148 149 C
(from water; published data [4]: mp 150 C).
I, Ar1 = Ar2 = C6H5; II, Ar1 = C6H5, Ar2 = 4-C6H5C6H4;
M = Li (a), Na (b).
High concentration of radical anions and homo-
geneity of the medium increase the probability of
collisions of electron-rich radical anion species with
electron-deficient carbon atom of carbon dioxide.
The absence among the products of oxalic acid which
could be formed via reductive dimerization of carbon
dioxide indicates that the process follows mainly the
The reaction of lithium diphenylketyl with carbon
dioxide was performed in a similar way. Yield of acid
III 46%, and of benzophenone, 49%.
-Hydroxy(phenyl)-4-biphenylylacetic acid (IV).
Sodium phenyl-4-biphenylylketyl (IIb) was prepared
1070-4280/01/3709-1344$25.00 2001 MAIK Nauka/Interperiodica