Synthesis, Resolution, and Aldol Reactions of a Planar-Chiral Lewis Acid Complex

The synthesis and resolution of a new planar-chiral Lewis acid complex is described. The compound is applied to asymmetric Mukaiyama aldol reactions, leading to the formation of the desired product with good stereoselectivity. The sense of stereoselection is as predicted by the design, which exploits the ability of the Lewis acid to simultaneously serve as a σ and a π acceptor. Mechanistic observations are consistent with rate-determining formation of an aldehyde−Lewis acid complex, followed by rapid nucleophilic addition.