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

A silica-supported chitosan-palladium complex has been found to catalyze th e asymmetric hydrogenation of some ketones to corresponding chiral alcohols , such as acetophenone to (R)-1-phenyl ethanol, propiophenone to (R)-1-phen yl-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 compl ex 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 10 0%, respectively. This chiral natural polymer-palladium complex catalyst wa s very easy to prepare, and could be reused without appreciable change in o ptical catalytic activity. (C) 1999 Elsevier Science B.V. All rights reserv ed.