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.