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 β,β-disubstituted enals and dioxindoles was developed, giving the spirocyclic oxindole-γ-lactones bearing two contiguous tetrasubstituted stereocenters in good yields with excellent diastereoselectivities and good enantioselectivities.