Diastereo- and Enantioselective Synthesis of Spirooxindoles with Contiguous Tetrasubstituted Stereocenters via Catalytic Coupling of Two Tertiary Radicals

The oxidative N-heterocyclic carbene-catalyzed [3 + 2] annulation of beta,beta-disubstituted enals and dioxindoles was developed, giving the spirocyclic oxindole-gamma-lactones bearing two contiguous tetrasubstituted stereocenters in good yields with excellent diastereoselectivities and good enantioselectivities.