Synthesis of Benzo[ b ]azepines via Intramolecular Cyclization of 2-Alkenyl- N -propargylanilines

Abstract An atom-economical and catalyst-free synthesis of benzo[b]azepines is described by tuning an intramolecular cyclization of 2-alkenyl-N-propargylanilines. The reaction was presumed to proceed through an in situ formation of aza-o-quinone methide (aza-o-QM), followed by 1,6-enyne cyclization under thermal conditions. The reaction exhibits a broad substrate scope upon validation of various alkynes, arenes, and amine components. The experimental and DFT studies provide mechanistic support for the proposed transformation and insights into the reaction pathway.