Construction of Nitrogen Heterocycles Bearing an Aminomethyl Group by Copper-Catalyzed Domino Three-Component Coupling−Cyclization

A direct approach to 2-(aminomethyl)indoles by copper-catalyzed domino three-component coupling−cyclization of 2-ethynylanilines with a secondary amine and aldehyde has been developed. By use of a cyclic or acyclic secondary amine and aldehyde (paraformaldehyde, aliphatic or aromatic aldehydes) in the presence of 1 mol % of CuBr, 2-ethynylanilines were converted to a variety of substituted 2-(aminomethyl)indoles in good to excellent yields. Utilizing this domino reaction and C−H functionalization at the indole C-3 position, polycyclic indoles were readily synthesized. Construction of benzo[e][1,2]thiazine and indene motifs by the reaction of sulfonamide and malonate congeners is also presented.