Rh(III)-Catalyzed Relay Double Carbenoid Insertion and Diannulation of Sulfoximine Benzamides with α-Diazo Carbonyl Compounds: Access to Furo[2,3-c]isochromenes.

An efficient rhodium-catalyzed construction of furo[2,3-c]isochromene scaffolds through tandem double carbenoid insertion and diannulation of sulfoximine benzamides with α-diazo carbonyl compounds has been developed. Mechanistic studies revealed that the alkyl-rhodium intermediate generated by carbenoid insertion was directly trapped with another molecule of carbene species, followed by subsequent intramolecular cyclization reactions. Sulfoximine was released in situ, featuring a traceless directing fashion. The reactions proceeded smoothly under mild conditions with wide functional group tolerance.