Enantioselective hydrogenation of methyl acetoacetate catalyzed by nickel supported on activated carbon or graphite

Heterogeneous enantioselective catalysts based on nickel, tartaric acid and NaBr supported on activated carbon or graphite were characterized and test ed in the asymmetric hydrogenation of methyl acetoacetate (MAX). Nickel cry stallite size depended on the type of carbon support, the preparation condi tions and reduction temperature of nickel. Enantioselectivity increased sig nificantly with increasing nickel crystallite size. High nickel loading (up to 85 wt.%) and large crystal size (<5000 <Angstrom>) were examined. Opera ting conditions such as temperature. hydrogen pressure and catalyst to subs trate ratio were varied over a wide range to achieve high enantiomeric exce ss values. Enantiomeric excess as high as 91% was obtained with nickel on g raphite. (C) 2001 Elsevier Science B.V. All rights reserved.