Highly Diastereo- and Enantioselective Palladium-Catalyzed [3+2] Cycloaddition of Vinyl Aziridines and α,β-Unsaturated Ketones

A palladium-catalyzed asymmetric [3+2] cycloaddition reaction of vinylaziridines with alpha,beta-unsaturated ketones, wherein the alkenes have a single activator, is realized in high diastereo- and enantioselectivity, thus affording 3,4-disubstituted pyrrolidines in high yields with excellent ee values. The introduction of a methyl group at C1 of the vinyl group the vinylaziridines greatly improves the stereochemistry of the reaction. A plausible transition state is proposed.