Enantioselective addition of diethylzinc to aldehydes using immobilized chiral BINOL–Ti complex on ordered mesoporous silicas

Abstract

A chiral (S)-BINOL ligand has been covalently grafted on ordered mesoporous silicas—MCM-41 and SBA-15 and the resulting inorganic–organic hybrid materials used as chiral auxiliaries in Ti-promoted enantioselective addition of diethyl zinc to aldehydes under heterogeneous conditions. These heterogeneous catalysts showed promising activity and enantioselectivity. The catalyst having a larger pore diameter with capping of free silanol moiety with trimethylsilyl (TMS) group was found to be more active with enantioselectivities up to 81% being achieved. The catalyst worked well up to three cycles with retention of enantioselectivity after washing with 10% HCl in methanol.