Direct synthesis of spirooxindoles enabled by palladium-catalyzed allylic alkylation and DBU-mediated cyclization: concept, scope and applications†

Developing new methods for the rapid synthesis of complex spirooxindole skeletons from simple feedstocks is highly desirable in the context of medicinal chemistry and drug discovery. Herein we disclosed an unprecedent and concise construction of spiro[indoline-3,2′-pyrrol]-2-one skeletons from vinyl benzoxazinanones and 3-isothiocyanato oxindoles. This process involves a palladium-catalyzed linear allylic alkylation, followed by a DBU-mediated intramolecular cyclization. The protocol is compatible with a wide range of substrates and affords structurally diverse spiro[indoline-3,2′-pyrrol]-2-ones in moderate to good yields under mild reaction conditions. Dichloromethane served both as solvent and reactant. Biological investigation revealed that one of the spiro[indoline-3,2′-pyrrol]-2-ones exhibited remarkable cytotoxicity towards SK-LU-1 human lung cancer cells. These spiro[indoline-3,2′-pyrrol]-2-ones not only enrich the library of spirooxindoles but also provide new opportunities for drug discovery.