Bifunctional Catalyst Applied to Enantioselective Organozinc Addition to Aldehydes

Abstract

The primary focus of this work is the synthesis of a new family of dipyridyl BINOL ligands. Their utility was demonstrated through the asymmetric addition of Et2Zn to aldehydes. The enantioselectivities obtained with L3 are comparable to or higher than those observed with similar BINOL-based ligands. A variety of ligands were readily prepared by a two-step sequence involving a directed ortho metallation to obtain 3, followed by a Negishi cross-coupling to give 4. The catalytic activity of L1-L3 proved to be best with conjugated aldehydes, as aliphatic substrates did not undergo alkylation.