L-Proline catalyzed four-component one-pot synthesis of coumarin-containing dihydropyrano[2,3-c]pyrazoles under ultrasonic irradiation

A simple and convenient approach to the synthesis of coumarin-containing dihydropyrano[2,3-c]pyrazoles via four-component reaction of beta-dicarbonyl compound, phenylhydrazine, aromatic aldehydes and malononitrile in EtOH catalyzed by L-proline under ultrasonic irradiation is described. The reaction gives the coumarin-containing dihydropyrano[2,3-c]pyrazoles in good to excellent yields at room temperature. This method provides several advantages, such as shorter reaction time, environmental friendliness, simple workup procedure and higher yields. (C) 2016 Elsevier Ltd. All rights reserved.