Asymmetric hydrogenation of ketones catalyzed by a silica-supported chitosan-palladium complex

A silica-supported chitosan-palladium complex has been found to catalyze the asymmetric hydrogenation of some ketones to corresponding chiral alcohols, such as acetophenone to (R)-1-phenyl ethanol, propiophenone to (R)-1-phenyl-1-propanol, 3-methyl-2-butanone to (R)-3-methyl-2-butanol, and 4-methyl-2-pentanone to (R)-4-methyl-2-pentanol at room temperature and under 1 atm H(2). The optical yield was greatly affected by N:Pd mole ratio in the complex and a little change in the structure of ketone. The optical yields of (R)-1-phenylethanol and (R)-3-methyl-2-butanol could be obtained in 99 and 100%, respectively. This chiral natural polymer-palladium complex catalyst was very easy to prepare, and could be reused without appreciable change in optical catalytic activity. (C) 1999 Elsevier Science B.V. All rights reserved.