Enantioselective hydrogenation of pyruvates over polymer-stabilized and supported platinum nanoclusters

The cinchonidine-modified enantioselective hydrogenation of pyruvates has b een studied over polyvinylpyrrolidone-stabilized platinum (PVP-Pt) and the corresponding alumina-supported platinum (Al2O3-Pt) clusters. It is shown t hat the catalysts with particle size less than 2.0 nm demonstrate >90% enan tioselectivity in favor of (R)-lactates. The solvent effect is similar to t hat over the conventional supported platinum catalyst except for tetrahydro furan. These colloidal and supported clusters are stable with no obvious lo ss of activity and enantioselectivity even after 18 months standing in air at room temperature. Molecular mechanics calculations of the modifier-react ant interaction on the platinum surface suggest that it is possible to obta in good enantioselectivity on the small clusters. (C) 1999 Elsevier Science Ltd. All rights reserved.