Decarbonylative Formation of Homoallyl Radical Capable of Annulation with N-Arylpropiolamides via Aldehyde Auto-oxidation.

A new metal-free aldehyde auto-oxidation strategy that allows the decarbonylative formation of homoallyl radical capable of cascade annulations with alkynes is described. By using various N-arylpropiolamides, the oxidative radical [3 + 2]/[5 + 2] cascade annulation reaction was achieved to produce benzo[ b]cyclopenta[ e]azepin-4(1 H)-ones, which represent a powerful new platform for the intermolecular cycloadditions of alkyne with broad substrate scope and high selectivity.