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

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