Novel binuclear chiral zirconium catalysts used in enantioselective Strecker reactions

A novel binuclear chiral zirconium catalyst was successfully used in enanti oselective Strecker reactions. The catalyst was readily prepared from zirco nium t-butoxide (Zr(OtBu)4), (R)-6,6'-dibromo-1,1'-bi-2-naphthol ((R)-6-Br- BINOL), and (R)-3,3'-dibromo-1,1'-bi-2-naphthol ((R)-3-Br-BINOL) to form un ique binuclear structure. It was revealed that a combination of (R)-6-Br-BI NOL and (R)-3-Br-BINOL was essential in these asymmetric reactions and that much lower selectivities were obtained by using other combinations. Two-co mponent (an imine and hydrogen cyanide (HCN)) and three-component (an aldeh yde, an amine, and HCN) Strecker reactions proceeded smoothly in the presen ce of a catalytic amount of the chiral zirconium catalyst to afford the cor responding alpha-amino nitrile derivatives in high yields with high enantio selectivities. (C) 2000 Wiley-Liss, Inc.