Pd-catalyzed decarboxylative [3+2] cycloaddition: Assembly of highly functionalized spirooxindoles bearing two quaternary centers

An efficient method for the practical formation of functionalized spirooxindoles, which was accompanied by generating a sterically congested spiroketal system and bearing two quaternary stereocenters via a sequential palladium, catalyzed decarboxylative [3 + 2] cycloaddition of vinylethylene carbonates (VECs) and isatins. Importantly, the redox-neutral catalytic system possesses the characteristics of operational convenience, good functional group tolerance, and good regioselectivity and diastereoselectivity, which enables a diastereoselective synthesis of spiroketal oxindole skeletons in an excellent yield.