New approach toward the synthesis of asymmetric heterogeneous catalysts for hydrogenation reactions

A new type of asymmetric heterogeneous catalysts is presented, together with results obtained in the enantioselective hydrogenation of ethyl pyruvate and acetophenone. The catalysts are prepared by using techniques derived from the surface organometallic chemistry on metals (reaction between a supported and a reduced transition metal catalyst with an organometallic compound). In the hydrogenation of acetophenone employing Pt-based catalysts, the presence of the organotin promoter notably enhances the chemoselectivity to phenylethanol (the desired product) in all cases. The enantioselective hydrogenation of acetophenone afforded an excess of the (S)-phenylethanol, with an enantiomeric excess (ee%) value of around 20% and a selectivity over 97%. Reusing of the catalysts is possible, keeping the selectivity and the ee% values.