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

摘要

Chiral Lewis acids serve as useful catalysts for a wide variety of powerful transformations,particularly addition reactions to aldehydes.Several years ago,we outlined a new approach to the design of a chiral Lewis acid,the distinguishing feature of which was a pi interaction between the Lewis acid and the carbonyl group (Figure 1).Since maximizing this overlap should enhance the electrophilicity of the aldehyde,this interaction could define the most reactive conformation of the Lewis acid-aldehyde complex.Because this design does not require a second functional group on the substrate in order to achieve conformational control of the complex,we anticipated that this approach might furnish an unusually versatile catalyst.