Facile synthesis of biologically active heterocycles by indium-induced reactions of aromatic nitro compounds in aqueous ethanol

Indium/ammonium chloride-induced reduction of aromatic nitro compounds to aromatic amines in aqueous ethanol was developed. Useful chemoselectivity was observed in the reduction reaction. This method was extended to reductive cyclization and rearrangement toward the synthesis of various biologically active heterocycles, including quinoline, oxazines, quinalonones, and phenanthridine in excellent yield. The oxophilicity of indium metal influenced the reaction in aqueous ethanol. Metals like zinc and tin were not effective in promoting this kind of reactions under the present environmentally friendly conditions.