Catalytic [4+2] Cyclization of α,β-Unsaturated Acyl Chlorides with 3-Alkylenyloxindoles: Highly Diastereo-and Enantioselective Synthesis of Spirocarboeyclic Oxindoles

摘要

The spirooxindole is a privileged structure moiety found in many biologically active natural products and pharmaceuti-cally active compounds. Thus, many elegant approaches have been developed for its construction. Typical intramolecular approaches are the oxidative rearrangement of tetrahydro-β-carbolines, and the palladium-catalyzed Heck reaction. The intermolecular cyclization, which forms two or more C—C bonds in one pot, is very interesting for the construction of cyclic compounds, because it is a step-economic approach and the starting materials are relatively readily available. Trost and co-workers reported a palladium-catalyzed [3+2] cyclization of 3-alkenyloxindole with trimethylenemethane, leading to the spirocyclic oxindolic cyclopentanes in good yields with high enantioselectivities. A facile synthesis of spirooxindole, developed by Carreira and co-workers, involves the formal [3+2] cyclization of spirocyclopropane with aldimines. Recently, several efficient routes to spirocyclic oxindole by the chiral amine-catalyzed cascade process were reported, including the [4+2] cyclization through double Michael addition, the [4+2] or [3+2] cyclization through Michael-aldol process, and the three-component [2+2+2] cyclization. Moreover, Lu and co-workers reported an interesting phosphine-cata-lyzed highly enantioselective [3+2] cyclization of 3-alkenyl-oxindoles with Morita-Baylis-Hillman adducts.