Copper-catalyzed synthesis of benzoxazoles via tandem cyclization of 2-halophenols with amidines

This work reports a simple, efficient and alternative synthetic route for the preparation of benzoxazoles via tandem cyclization of 2-halophenols with amidines. The developed methodology is free from ligands and uses inexpensive and easily available CuCl as a catalyst. This protocol avoids the use of any oxidant or inorganic acids. Various benzoxazole derivatives were synthesized in good to excellent yields. To the best of our knowledge, this is the first time that the synthesis of benzoxazoles from 2-halophenols with both aromatic and aliphatic amidines is reported. Owing to the simplicity of this protocol, the preparation of benzoxazoles could be achieved at a gram scale level.