New condensation of potassium diphenylketyl and its dianion with aniline

Full text of DOI:10.1023/A:1022586707054

Russian Journal of Organic Chemistry, Vol. 38, No. 11, 2002, pp. 1691 1692. Translated from Zhurnal Organicheskoi Khimii, Vol. 38, No. 11, 2002,
pp. 1748 1749.
Original Russian Text Copyright
2002 by Turaeva, Kurbatov.
SHORT
COMMUNICATIONS
New Condensation of Potassium Diphenylketyl and Its Dianion
*
with Aniline
D. A. Turaeva and Yu. V. Kurbatov
Alisher Navoi Samarkand State University, Samarkand, 703004 Uzbekistan
Received January 15, 2002
We found formerly that metal ketyls and dianions
of benzophenone were capable of radical-anion sub-
stitution [1 4], and K-derivatives also participated
in radical-anion disproportionation [5 7].
the final product of this base-acid reaction, benz0
hydrol (IV), formed in trace amounts. Moreover, this
process is not characteristic even for benzophenone
dianion which alongside an alkoxide basic site has a
more active carbanion site.
In continuation of these studies we investigated
reactions between K-ketyl (Ia) and K-dianion (Ib)
of benzophenone with aniline (II) and instead of
radical-anion diphenyloxymethylation providing the
corresponding substitution products we observed a
condensation resulting in diphenylmethineaniline (III)
in relatively high yield (70 and 44% respectively).
Obviously in the key stage of C N bond formation
participate both anilide-anion and benzophenone. This
is confirmed by the fact that this stage is common for
the condensation mechanism of carbonyl compounds
with amines catalyzed by bases [13], and by carrying
out reaction of separately prepared potassium anilide
with benzophenone under identical conditions and
obtaining anil III in high yield (83%).
The reaction takes place in a solvating medium (in
tetrahydrofuran) at room temperature and is accom-
panied by hydrogen liberation. As side reactions
should be mentioned the reduction to benzhydrol (IV)
and the cleavage with formation of benzoic acid (V).
The lower yield of the final product with dianion
Ib rules out its presence as an intermediate form
generated by disproportionation in the reaction of
radical-anion Ia [8].
The first stage of the reaction consists in aniline
metallation where aniline plays the role of NH-acid,
and the benzophenone radical-anion is the base
providing an active electron in one-electron transfer
process [9] resulting in the observed release of hydro-
gen. Such transfer occurred in aniline reaction even
with a less active metal, sodium [10], and also in a
model reaction when we treated aniline with potas-
sium under the conditions in question.
The discovered condensation may serve for
development of a novel and sufficiently effective
synthetic procedure for Schiff bases (especially with
aromatic ketones and amines) that is distinguished by
the use instead of weakly active ketones [14] a lot
more reactive stable ketyls or dianions. The latter
ensures considerably milder reaction conditions
Radical-anions are particular bifunctional bases:
firstly, as donors of weakly bound active electron [9],
and secondly, as proton acceptors [11, 12]. However
benzophenone-potassium ketyl hardly behaved in this
system and under these conditions as proton acceptor:
(
room temperature, no catalyst) and sufficient yields
of the target products.
Reaction of benzophenone-potassium ketyl (Ia)
with aniline (II). To a solution of benzophenone-
potassium ketyl prepared from 4.55 g (0.025 mol) of
benzophenone (I) and 1 g (0.025 mol) of finely cut
*
The study was carried out under financial support of the
Ministry of Higher Education and the Foundation of Basic
Research of Uzbekistan Republic (program 5F).
1
070-4280/02/3811-1691$27.00 2002 MAIK Nauka/Interperiodica

1
692
TURAEVA, KURBATOV
potassium in 80 ml of anhydrous THF in a stream of
purified dry nitrogen was added 4.6 g (0.05 mol) of
amine II dissolved in 20 ml of THF. The color of the
reaction mixture changed from blue to dark brown,
and hydrogen evolution was observed. After 24 h
water was poured to the reaction mixture, the separat-
ed yellow precipitate was filtered off. We obtained
2. Kurbatova, A.S., Kurbatov, Yu.V., Niyazova, D.A.,
and Atayan, P.S., Zh. Org. Khim., 1984, vol. 20,
no. 1, pp. 187 190.
3. Kurbatov, Yu.V., Kurbatova, A.S., and Niyazo-
va, D.A., Abstracts of Papers, 6th International
Conference on Organic Synthesis, Moskow, 1986,
p. 222.
4. Turaeva, D.A., Kurbatova, A.S., and Kurba-
tov, Yu.V., Zh. Org. Khim., 1993, vol. 29, no. 8,
pp. 1588 1591.
3
.5 g of diphenylmethineaniline (III). R 0.62 (TLC,
f
Al O of II activity grade, eluent benzene hexane,
2
3
1
: 1, development in iodine vapor), mp 117 C (from
acetone) [14]. The mixed sample with authentic
diphenylmethineaniline prepared by procedure [14]
melted without depression of the melting point. From
the water-tetrahydrofuran mixture by extraction with
ether was additionally separated 1 g of azomethine
III, overall yield 70%. From the ether mother liquor
was isolated 0.8 g (18%) of benzophenone. From the
water solution after acidifying with dilute (1: 1)
hydrochloric acid we isolated 0.6 g (20%) of benzoic
acid (V), mp 121 C.
5. Turaeva, D.A., Kurbatov, Yu.V., and Muratova, C.,
Abstracts of Papers, 12th International Conference on
Organic Synthesis, Venezia, Italy, 1998, p. 390.
6. Turaeva, D.A. and Kurbatov, Yu.V., Zh. Org. Khim.,
1999, vol. 35, no. 7, pp. 1116 1117.
7. Turaeva, D.A., Kurbatova, A.S., and Kurba-
th
tov Yu.V., Abstracts of Papers, 10 IUPAC Sym-
posium on Organometallic Chemistry Directed
Towards Organic Synthesis, Versailles, France, 1999,
p. 490.
8
9
. Bachmann, V.E., J. Am. Chem. Soc., 1933, vol. 55,
pp. 2827 2830.
. Okhlobystin, O.Yu., Perenos elektrona v organiche-
skikh reaktsiyakh (Electron Transferr in Organic
Reactions), Riga Gos. Univ., 1974, p. 48.
Reaction of benzophenone-potassium dianion
Ib) with aniline (II). Benzophenone-potassium
(
dianion was prepared from 4.55 g (0.025 mol) of
benzophenone (I) and 2 g (0.05 mol) of finely cut
potassium in 80 ml of anhydrous THF in a tightly
stoppered flask. After complete dissolution of the
metal (in two weeks) to the violet solution obtained in
a stream of purified dry nitrogen was added 4.65 g
1
1
0. Foerst, W., Newer Methods of Preparative Organic
Chemistry, New York Acad., 1963, p. 246.
,
1. Mendkovich, A.S. and Gul tyai, V.P., Teoreticheskie
osnovy khimii organicheskikh anion-radikalov
(
0.05 mol) of amine II dissolved in THF. Further
(
Theoretical Principles of Anion-Radocal Organic
work-up was carried out as described for the reaction
with ketyl (Ia). We obtained 1.9 g (44%) of diphenyl-
methineaniline (III), 0.7 g (15%) of benzophenone
Chemistry), Moscow: Nauka, 1990.
1
1
2. Todres, Z.V., Ion-radikaly v organicheskom sinteze
(
Ion-Radicals in Organic Synthesis), Moscow: Khi-
(
(
I), 33% of benzoic acid (V), and 5% of benzhydrol
IV).
miya, 1986, p. 20.
3. Denisov, E.T., Kinetika gomogennykh khimicheskikh
reaktsii (Kinetics Homogeneous Chemical Reactions),
Moscow: Vysshaya shkola, 1978, p. 127.
REFERENCES
1
. Kurbatova, A.S., Kurbatov, Yu.V., and Niyazo-
14. Billman, J.H. and Tai, K.M., J. Org. Chem., 1958,
va, D.A., Zh. Org. Khim., 1979, vol. 15, no. 9, p. 2004.
vol. 23, p. 535.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 38 No. 11 2002