Chiral-Boron-Complex-Catalyzed Asymmetric [3+2] Cycloaddition of β-Trifluoromethyl α,β-Unsaturated Ketones with N,N′-Cyclic Azomethine Imines

The (R)-3,3 '-(3,5-(CF3)2-C6H3)2-BINOL-boron-complex-catalyzed asymmetric 1,3-dipolar cycloaddition of beta-trifluoromethyl alpha,beta-unsaturated ketone with N,N '-cyclic azomethine imines was developed to afford N,N '-bicyclic pyrazolidine derivatives bearing a stereogenic carbon center containing CF3 motifs in high yields with excellent diastereo- and enantioselectivities (up to >20:1 dr, and >99% ee). This catalytic system features mild reaction conditions, high efficiency, and a broad substrate scope.