Copper(I)-Catalyzed Synthesis of Benzoxazoles and Benzimidazoles

Significance

Reported is a synthesis of benz­oxazoles and benzimidazoles by a ligand-free copper-catalyzed C-N coupling-cyclization reaction of ortho-halophenols with ortho-haloanilines. Among the copper sources, CuI showed the highest catalytic activity. Polar solvents, for example MeCN, were shown to give higher yields of products than unpolar solvent, for example toluene. The N,N-dimethyl­glycine ligand was shown to afford a slightly higher yield under the same reaction conditions. A mechanism of sequential phenol and aniline addition to carbodiimide followed by intra­molecular C-N coupling was proposed without verification.