Copper-catalyzed N-arylation of heterocycles in ethylene glycol medium

N-Aarylation of imidazole, benzimidazole, pyrazole, and indole was performed in the presence of CuI as the catalyst and NaOH as the base in ethylene glycol medium. Apparently, ethylene glycol played a dual role as both the reaction solvent and a ligand for the catalyst. All reactions proceeded selectively to give the corresponding N-arylated products. In some cases, O-alkylation or dehalogenation was observed which was explained by the proposed catalytic cycle. Conventional heating at 120 oC and microwave irradiation both were used, where the results showed that microwave irradiation could facilitate the reaction by lowering the reaction times and increasing the yields. The reaction medium was recovered and reused in several consecutive runs.