A Simple and Efficient One-Pot Multicomponent Ceric Ammonium Nitrate-Catalyzed Synthesis of 5-Methyl-3-(2-arylimidazo[4,5-b]indol-3-yl)isoxazoles in Aqueous Ethanol

Fused imidazoindole frameworks are significant moieties found in many natural products and pharmacologically active compounds. In this context, a simple and efficient protocol for the synthesis of novel 2-arylimidazo[4,5-b]indol-3-ylisoxazoles via a multicomponent reaction of 5-methylisoxazol-3-amine, an aromatic aldehyde, ammonium acetate, and a substituted isatin in the presence of ceric ammonium nitrate as a catalyst in aqueous ethanol as a green solvent has been developed. The main advantages of this procedure are high yields, operational simplicity, easy workup, an inexpensive and commercially available catalyst, and an environmentally benign solvent. The products are isolated in pure form by recrystallization, which makes the method practical and facile.