Stereoselective Construction of Unsymmetrically Linked Heterocycles via Palladium-Catalyzed Alkyne Insertion/Cycloimidoylation Cascade

A novel strategy to access unsymmetrically linked heterocycles via palladium-catalyzed acylcycloimidoylation of alkyne-tethered carbamoyl chlorides with isocyanides has been developed. Functionalized isocyanides were successfully applied as imine-containing heterocycle precursors to capture the vinyl-Pd intermediate, which was generated from a syn-carbopalladation of alkyne, followed by subsequent intramolecular C-H bond activation/imidoylative Heck reactions. Methylene oxindoles within -tetrasubstituted olefins were obtained in high yields with excellent stereoselectivities. Broad functional groups were well tolerated under mild reaction conditions.