InCl-catalyzed one-pot synthesis of multi-substituted pyrano[2,3-c]pyrazole-4-carboxylic acid esters under ultrasound irradiation.

An efficient and simple procedure for the synthesis of 6-amino-5-cyano-4-phenyl-pyrano[2,3-c]pyrazole-4-carboxylic acid esters was developed via a one-pot reaction of β-ketoester, hydrazine, benzoylacetate, and malononitrile in 50% EtOH catalyzed by InCl under ultrasound irradiation. This method is more economic, convenient, nontoxic, and environmentally friendly than established methods of pyranopyrazole synthesis. Target compounds were obtained in excellent yields of up to 95%.