Chriral proline-derivative anchored on mesoporous silicas and their application to the asymmetric diethylzinc addition to benzaldehyde

Abstract

We developed new heterogeneous catalysts employing a proline-derived ligand immobilized on mesoporous silicas (MCM-41 and SBA-15) and they were applied to asymmetric diethylzinc addition to benzaldehyde. The reaction enantioselectivity was found to be largely dependent upon the pore size of the mesoporous silicas, capping of free silanol moiety with trimethylsilyl (TMS) group and employment of n-BuLi. High enantioselectivity (75% e.e.) was achieved when both TMS capping and n-BuLi addition were applied for the large pore-sized SBA-15 based catalyst. (C) 2001 Elsevier Science B.V. All rights reserved.