Indium chloride (InCl3) catalysed domino protocol for the regioselective synthesis of highly functionalized pyranopyrazoles under mild conditions

Regioselective synthesis of highly functionalized pyranopyrazoles was achieved in excellent yield from phenyl pyrazolone, substituted aromatic aldehyde with nitroketene-N,S-acetal in the presence of indium trichloride as a versatile catalyst under reflux condition in ethanol-water mixture. All reactions proceeded within a short period of time with excellent purity. All of the synthesized compounds were identified by IR, ^1H NMR, ^13C NMR and mass spectroscopy. Quantitative yields, inexpensive and environmentally friendly solvent system and simple work-up procedure are the attractive features of the present method. It is thus enviro-economic method without producing hazardous wastes. The formed pyranopyrazoles might find to possess important biological and pharmaceutical applications.