Synthesis of Oxindole and β-Lactam Spiro-ethers

Significance

The authors describe the development of an unprecedented domino sequence, consisting of the spirocyclization of α-allenols and cross coupling (Heck, Sonogashira, Suzuki-Miyaura reactions) leading to the formation of substituted spirolactams. The reaction is suggested to proceed by a series of steps involving the formation of a palladium-allene complex followed by an intramolecular oxopalladation by the hydroxyl group, affording a spirocyclic vinylic palladium species. The final step is the reaction of the vinyl Pd species in Heck, Sonogashira and Suzuki-Miyaura cross-coupling reactions to provide the diverse spirolactam products.