Harnessing In Situ Radical Oxygenation: Copper-Catalyzed Interrupted Azirine-Alkyne Ring-Expansion Reaction for the Synthesis of Pyrrolones.

Here we report a novel interrupted azirine-alkyne ring-expansion reaction with molecular oxygen for the direct synthesis of highly functionalized pyrrolones enabled by copper catalysis. Mechanistic investigations indicate that the present three-component reaction proceeds via two copper-catalyzed sequential reactions, an azirine-ring-opening alkynylation and an amine-directed radical oxygenation, leading to the formation of interesting pyrrolone structures under mild conditions.