Enantioselective hydrogenation of pyruvic acid oxime to alanine on Pd/alumina

被引:45
作者
Borszeky, K [1 ]
Mallat, T [1 ]
Aeschiman, R [1 ]
Schweizer, WB [1 ]
Baiker, A [1 ]
机构
[1] ETH ZENTRUM,DEPT CHEM ENGN & IND CHEM,CH-8092 ZURICH,SWITZERLAND
关键词
D O I
10.1006/jcat.1996.0203
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
The chemo- and enantioselective hydrogenation of pyruvic acid oxime have been studied on Pd/alumina, the latter in the presence of the 1,2-amino alcohol type alkaloids ephedrine, cinchonidine, and cinchonine. High yields of racemic alanine (90-98%) were obtained in the absence of alkaloids in polar solvents at 0-45 degrees C and 10 bar. Enantioselection increased with higher temperature and alkaloid:oxime molar ratio, A 1:1 ephedrine:oxime molar ratio afforded the best enantiomeric excess (26%). The presence of alkaloid resulted in a decrease of reaction rate by a factor of up to 140, compared to the racemic hydrogenation. Based on X-ray crystal structure analysis of the alkaloid-pyruvic acid oxime adduct, a mechanism is proposed for the steric course of the reaction. Extended interactions by multiple H bonds between the adsorbed alkaloid-oxime salt units on the Pd surface is assumed to be at the origin of the moderate enantioselectivity and the very low enantioselective hydrogenation rate. (C) 1996 Academic Press, Inc.
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页码:451 / 458
页数:8
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