Cooperative Anion−π Catalysis with Chiral Molecular Cages toward Enantioselective Desymmetrization of Anhydrides

Abstract

Exploiting novel noncovalent interactions for catalysis design represents a fascinating direction. For the flexible and relatively weak anion−π interactions, manipulation of two or more π-acidic surfaces for cooperative activation is highly desirable. Here, we demonstrate the strategy of cooperative anion−π catalysis based on chiral molecular cages with V-shaped electron-deficient cavities for synergic binding and activation of dicarbonyl electrophiles toward highly enantioselective desymmetrization transformation. The chiral cages were readily synthesized by incorporation of additional chiral base sites in one step. The cages efficiently catalyzed methanolytic desymmetrization of a series of meso cyclic anhydrides in nearly quantitative yields and up to 94% ee. In contrast, the non-cage analogues and simple control catalysts showed sluggish conversion and much lower enantioselectivity. Crystal structure, substrate binding studies, and theoretical modeling consistently suggested the essential role of the cage electron-deficient cavities in harnessing cooperative anion−π interactions for efficient activation and excellent selectivity control.