From Highly Enantioselective Monomeric Catalysts to Highly Enantioselective Polymeric Catalysts: Application of Rigid and Sterically Regular Chiral Binaphthyl Polymers to the Asymmetric Synthesis of Chiral Secondary Alcohols

Abstract

A 1,1‘-binaphthyl-based polymeric chiral catalyst with the most general enantioselectivity for the alkylzinc addition to a broad range of aldehydes has been obtained. This polymer can be easily recovered, and the recycled polymer shows the same catalytic properties as the original polymer. A highly enantioselective catalytic diphenylzinc addition to aldehydes has also been achieved by using the chiral binaphthyl monomer and polymer catalysts. Particularly, the excellent enantioselectivity observed for the addition of diphenylzinc to aromatic aldehydes allows the preparation of optically active diaryl carbinols that are synthetically useful but difficult to access by asymmetric catalysis. A novel asymmetric reduction of ketones catalyzed by the mono- and polybinaphthyl zinc complexes has been discovered. Our work on the asymmetric organozinc addition to aldehydes and the asymmetric reduction of ketones catalyzed by the zinc complexes of chiral binaphthyl monomer (R)-12 and polybinaphthyl (R)-43 has not onl...