Bifunctional Catalyst Applied to Enantioselective Organozinc Addition to Aldehydes

Significance

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.