Application of chiral poly binaphthyl-based Lewis acid catalysts to the asymmetric. organozinc additions to aldehydes

A systematic study of novel rigid and sterically regular chiral binaphthyl polymer-based Lewis acid catalysts has been carried out. Through this study, a polymeric chiral Lewis acid catalyst with the most general enantioselectivity for the reaction of aldehydes with diethylzinc has been obtained. This polymer-based catalyst also shows high enantioselectivity for the reaction of other alkyl or aryl zinc reagents with aldehydes. The polymer ligands used in these reactions can be easily recovered after the reaction and the recovered ligands show the same catalytic properties as the original polymers. This work not only provides highly enantioselective methods to prepare optically active secondary alcohols, but also establishes new strategies to design and synthesize polymeric chiral catalysts. The sterics and electronics of the catalytic sites in these rigid and sterically regular polymers can be systematically modified. The rigid polymer structure can also be used to preserve the catalytic properties of monomer catalysts provided that the catalytically active species are monomeric rather than monomer aggregates.