Umpolung of Imines Enables Catalytic Asymmetric Regio-reversed [3+2] Cycloadditions of Iminoesters with Nitroolefins

A copper-catalyzed regio-reversed asymmetric [3+2] cycloaddition of iminoesters with nitroolefins is disclosed for the first time. This method enables the facile synthesis of polysubstituted chiral pyrrolidines bearing at least one chiral quaternary center in high yields with excellent regio-, diastereo-, and enantioselectivity. The application of chiral P,S ligands and the unique effect of alpha-aryl groups on the iminoesters are key to the success of this method. The practicality and versatility of the reaction are also demonstrated.