Kinetic Resolution of Aziridines Enabled by N-Heterocyclic Car-bene/Copper Cooperative Catalysis: Carbene Dose-Controlled Chemo-Switchability.

Asymmetric methods that convert racemic starting materials to enantioenriched products are inherently significant in chemical synthesis. Catalytic kinetic resolution (KR) and dynamic kinetic asymmetric transformation (DyKAT) are alternative and complementary avenues to access chiral stereoisomers of both starting materials and reaction products. The development of highly efficient chiral catalytic systems for kinetically controlled processes has therefore been one of the linchpins in asymmetric synthesis. N-Heterocyclic carbene (NHC)/copper cooperative catalysis has enabled highly efficient KR and DyKAT of racemic N -tosylaziridines via [3 + 3] annulation with isatin-derived enals, leading to highly enantioenriched N -tosylaziridine derivatives (up to >99% e.e.) and a large library of spirooxindole derivatives with high structural diversity and stereoselectivity (up to >95:5 d.r., >99% e.e.). Mechanistic studies suggest that NHC can bind reversibly to the copper catalyst without compromising its catalytic activity and regulate the catalytic activity of the copper complex to switch the chemoselection between KR and DyKAT.