Highly Enantioselective [3+2]-Annulation of Isatin-Derived Morita-Baylis-Hillman Adducts with Cyclic Sulfonimines

An organocatalytic [3 + 2]-annulation between isatin-derived Morita-Baylis-Hillman adducts and cyclic sulfonimines has been developed in high yields with excellent enantio- and diastereoselectivities via an allylic nitrogen-ylide intermediate. The reaction provides access to heavily substituted aza-spirooxindole derivatives, which also contain ring fused cyclic sultams.