CuBr-Catalyzed Coupling of N-Tosylhydrazones and Terminal Alkynes: Synthesis of Benzofurans and Indoles

A new method for the synthesis of benzofurans or indoles via ligand-free CuBr-catalyzed coupling/cyclization of terminal alkynes with N-tosylhydrazones derived from o-hydroxy- or o-aminobenzaldehydes has been developed. A wide range of functional groups were found that are able to tolerate the reaction conditions.