Stereoselective Construction of α-Tetralone-Fused Spirooxindoles via Pd-Catalyzed Domino Carbene Migratory Insertion/Conjugate Addition Sequence.

An efficient diastereoselective synthesis of α-tetralone-fused spirooxindoles is reported. The Pd-catalyzed domino reaction proceeds through a carbene migratory insertion followed by a 6-endo-trig mode of conjugate addition sequence from easily accessible isatin-derived N-tosylhydrazones and 2'-iodochalcones. The versatility of the protocol has been showcased by high functional group tolerance, broad substrate scope, and extension to an expedient synthesis of spiroacenaphthylenes. NMR reaction profiling and deuterium-labeling investigations provide insight into the mechanistic pathway.