Facile synthesis of benzoindoles and naphthofurans through carbonaceous material-catalyzed cyclization of naphthylamines/naphthols with nitroolefins in water.

A facile and efficient approach has been established for the synthesis of benzoindole and naphthofuran derivatives via the metal-free cyclization reaction of nitroolefins with naphthylamines/naphthols. Various substituted benzoindoles and naphthofurans are obtained in good to excellent yields. Moreover, the ability to recycle the carbonaceous material makes this method quite cost-effective and environmentally benign compared to traditional acid-catalyzed methods. Theoretical studies indicated that the reaction between naphthylamine and nitroolefin catalyzed by this solid acid was thermodynamically controlled at 60 °C, resulting in the formation of the benzoindoles.