Palladium-Catalyzed Photoredox Aminocarbonylative [3 + 2 + 1] Heteroannulation of Propargyl Acetates with α-Aminoazoles and CO

We report a palladium-catalyzed photoredox aminocarbonylative [3 + 2 + 1] heteroannulation of propargyl acetates with α-aminoazoles and CO for the synthesis of 5H-oxazolo[3,2-a]pyrimidin-5-ones, 5H-thiazolo[3,2-a]-pyrimidin-5-ones, 4H-benzo[4,5]oxazolo[3,2-a]pyrimidin-4-ones, 4H-benzo[4,5]thiazolo[3,2-a]pyrimidin-4-ones, and benzo[4,5]-imidazo[1,2-a]pyrimidin-4(10H)-ones. This reaction features a wide functional group compatibility and a broad substrate scope and is highlighted with its successful applicability to complex molecule late-stage modifications. Mechanistic study reveals that the Pd(OAc)₂/DPEPhos system serves as the photocatalyst, and the key excited-state [Pd(OAc)₂/DPEPhos]* irradiated by visible light is intercepted with propargyl acetates to generate the propargyl radicals, followed by isomerization and insertion of CO, to afford the carbonyl radicals, radical polar crossover, allene nucleophilic hydroamination, and isomerization cascades.