Synthesis and Applications of Chiral Bicyclic Bisborane Catalysts

Abstract The development of chiral borane Lewis acid catalysts opened the door for transition-metal-free catalyzed asymmetric organic reactions. Herein, we have summarized our work on the preparation of two classes of novel chiral bicyclic bisborane Lewis acid catalysts derived from C 2-symmetric [3.3.0] dienes and [4.4] dienes, respectively. These catalysts not only form frustrated Lewis pairs with Lewis bases to catalyze asymmetric hydrogenation reactions but also activate Lewis basic functional groups in traditional Lewis acid catalyzed asymmetric reactions. 1 Introduction 2 Synthesis of C 2-Symmetric Fused Bicyclic Bisborane Catalysts and Their Use in Imine Hydrogenation 3 Synthesis of Spiro Bicyclic Bisborane Catalysts and Their Use in ­N-Heteroarene Reduction 4 Other Types of Asymmetric Reactions Promoted by Chiral ­Bicyclic Bisborane Catalysts 5 Conclusion