Russian Journal of Organic Chemistry, Vol. 39, No. 5, 2003, p. 735. Translated from Zhurnal Organicheskoi Khimii, Vol. 39, No. 5, 2003, p. 782.
Original Russian Text Copyright
2003 by S. Shchelkunov, Do, Bekenova, A. Shchelkunov.
SHORT
COMMUNICATIONS
Chemical Aspects of Electrocatalytic Reduction
of Carbonyl Compounds. Aldehydes
S. A. Shchelkunov, S. V. Do, U. B. Bekenova, and A. V. Shchelkunov
Cherepovets State University, pr. Pobedy 12, Cherepovets, 162606 Russia
Received November 19, 2002
In continuation of our studies on electrocatalytic
reduction of carbonyl compounds in alkaline medium
over Raney nickel [1], we examined the reduction of
a series of aldehydes. The hydrogenation of benzalde-
hyde, which is incapable of undergoing aldol con-
densation, gave benzyl alcohol. The reaction with
isobutyraldehyde under the same conditions led to
aldol condensation and subsequent hydrogenation of
the resulting -hydroxy aldehyde to afford 2,2,4-tri-
methylpentane-1,3-diol in high yield.
Reduction of benzaldehyde. As anolyte we used
50 ml of 20% aqueous sodium hydroxide. Raney
nickel, 0.5 g, was placed in the cathode chamber
together with 50 ml of 5% aqueous sodium hydroxide.
The reduction was performed at 20 C at a constant
current (1 A, 8 V). Before addition of benzaldehyde,
the catalyst was saturated with hydrogen over a period
of 20 min. Benzaldehyde, 5 ml (5.2 g, 0.05 mol), was
then added, and the electrocatalytic reduction was
conducted for 2 h. When the reaction was complete,
the products were extracted from the catholyte with
diethyl ether, and volatile fractions were distilled off
from the extract. According to the GLC data, the yield
of benzyl alcohol was 96% (current-based yield 75%).
From isobutyraldehyde and butyraldehyde we ob-
tained, respectively, 2,2,4-trimethylpentane-1,3-diol
(
2
chemical yield 92%, current-based yield 65%) and
-ethylhexane-1,3-diol (chemical yield 90%, current-
based yield 62%). In the synthesis of 1,3-butanediol
from acetaldehyde, the chemical yield was 85%, and
current-based yield, 62%. In the reduction of croton-
aldehyde, the chemical yield was 80%, and current-
based yield, 63%.
The products were identified by GLC on a Chrom-5
chromatograph using authentic samples; thermal con-
ductivity detector, carrier gas helium (80 ml/min),
glass column (3500 3 mm), stationary phase 5% of
polyethylene glycol on Chromaton N-AW-DMCS,
oven temperature 80 C.
The concentration of 2-methyl-1-propanol in the
products was as low as 2.6%. The reduction of acet-
aldehyde and butyraldehyde followed an analogous
pattern. The hydrogenation of crotonaldehyde also
involved intermediate formation of -hydroxy alde-
hyde and gave the same product as that obtained from
acetaldehyde, 1,3-butanediol.
The electrocatalytic reduction was carried out in
a two-chamber electrolyzer whose anode and cathode
chambers were separated by an MA-40 ion exchange
membrane. The cathode chamber was equipped with
a stirrer operating at a speed of 300 rpm. A platinum
network was used as anode, and a titanium plate, as
cathode.
REFERENCE
1. Shchelkunov, S.A., Mazakova, S.V., Bekenova, U.B.,
Amirkhanova, A.K., and Shchelkunov, A.V., Russ. J.
Org. Chem., 2001, vol. 37, p. 446.
1
070-4280/03/3905-0735$25.00 2003 MAIK Nauka/Interperiodica