Chiral-Boron-Complex-Catalyzed Asymmetric [3 + 2] Cycloaddition of 2'-Hydroxychalcones with N , N '-Cyclic Azomethine Imines.

We report the ( R )-3,3'-I 2 -BINOL-boron-complex-catalyzed asymmetric 1,3-dipolar cycloaddition of 2'-hydroxychalcones with N , N '-cyclic azomethine imines, providing the corresponding N , N '-bicyclic pyrazolidine derivatives with three contiguous tertiary stereocenters in high yields with excellent diastereo- and enantioselectivities (up to >99:1 diastereomeric ratio and >99% enantiomeric excess). This catalytic system exhibits advantages of mild reaction conditions, high efficiency, and broad substrate scopes.