Chemistry of Heterocyclic Compounds, Vol. 37, No. 10, 2001
SYNTHESIS OF O,C-DILITHIUM
DERIVATIVES OF 2-(α-HYDROXYALKYL)-
1-METHYLBENZIMIDAZOLES
A. S. Morkovnik and B. A. Tertov
Keywords: benzimidazoles, lithium arenes, lithium organic compounds.
Diazoles and their halo derivatives form lithium organic compounds upon the action of lithium salts of
arene radical–anions, in particular, lithium naphthalene [1, 2]. We have found that 2-acylbenzimidazoles react
readily with lithium naphthalene to give O,C-dilithium derivatives, corresponding to a two-electron reduction of
the substrates. Thus, 2-formyl-1-methyl- (1a) and 2-acetyl-1-methylbenzimidazoles (1b) react with lithium
naphthalene in THF to give dilithium derivatives 2a and 2b, which undergo hydrolysis to give 2-hydroxymethyl-
) and 2-(α-hydroxyethyl)-1-methylbenzimidazoles (
1-methyl- (3a
with benzaldehyde gives diols 4a and 4b.
3b), respectively. The reaction of 2a and 2b
N
N
O
R
_
+
2C10H8
Li , +2e
Me
1a,b
OH
H
N
N
H2O
R
OLi
Li
N
R
Me
3a,b
N
Me
PhCHO
OH
H
OH
R
N
N
2a,b
Ph
Me
4a,b
a R = H, b R = Me
1-(1-Methyl-1H-benzimidazol-2-yl)-2-phenylethane-1,2-diol (4a).
A
sample of 2-formyl-1-
methylbenzimidazole (1.5 g, 9.4 mmol) in THF (10 ml) was added with stirring to a solution of lithium
naphthalene obtained from naphthalene (3.6 g, 28.8 mmol) and lithium (0.2 g, 28.8 mmol) in THF (30 ml) at
0°C over 10 min and then, benzaldehyde (3.0 g, 28.3 mmol) in THF (10 ml) was added over 10 min. After
15 min, the mixture was hydrolyzed and the bases were extracted with a 1:1 mixture of conc. hydrochloric acid
and water and, then, 1.7 g (68%) diol 4a was isolated by the ordinary procedure; mp 177-180°C (acetonitrile).
__________________________________________________________________________________________
Physical and Organic Chemistry Research Institute, Rostov-on-Don State University, 344090
Rostov-on-Don, Russia; e-mail: asmork@ipoc.rsu.ru. Translated from Khimiya Geterotsiklicheskikh Soedinenii,
No. 10, pp. 1419-1420, October, 2001. Original article submitted May 29, 2001.
1302
0009-3122/01/3710-1302$25.00©2001 Plenum Publishing Corporation