Effects of reaction variables on enantioselectivity of modified Raney nickel catalyst

The effects of reaction variables (temperature, pressure, solvent type, substrate to catalyst ratio and substrate concentration) on enantioselectivity of methyl acetoacetate hydrogenation were studied. Raney nickel modified with (2R,3R)-(+)-tartaric acid was used as a catalyst. The reactions were carried out in a liquid phase, under atmospheric and increased hydrogen pressure. It was found that the reaction variables have a significant effect on the resulting enantioselectivity. Adecrease of enantioselectivity either occurred at low substrate concentration in the reaction mixture or related to a catalyst. Changes of enantioselectivity were monitored during the reaction. The highest values of enantioselectivity were achieved under high hydrogen pressures (10 MPa), at a temperature of 60 degreesC and with tetrahydrofuran as the solvent. (C) 2002 Elsevier Science B.V. All rights reserved.