Hydroxyl-Directed Iridium-Catalyzed Synthesis of Pyrano[2,3,4-de]chromen-2-ones and Further Chalcogenation under Blue-Light Irradiation

The hydroxyl-directed iridium-catalyzed peri-selective C-H bond activation to synthesize substituted pyrano[2,3,4-de]chromen-2-ones and further chalcogenylation under blue light irradiation has been realized efficiently. Most products of polycyclic pyrans and corresponding chalcogenated derivatives with various substituents were achieved in good to excellent yields. Preliminary mechanistic studies suggest that this transformation may pass through a five-membered iridacycle intermediate containing an O-Ir sigma-bond and a photocatalytic free radical process.