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

We report the (R)-3,3′-I2–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.