A novel and environment-friendly method for preparing dihydropyrano[2,3-c]pyrazoles in water under ultrasound irradiation

A green and convenient approach to the synthesis of dihydropyrano[2,3-c]pyrazoles via four-component reaction of aromatic aldehydes, hydrazine. ethyl acetoacetate and malononitrile in water under ultrasound irradiation is described. This method provides several advantages such as environmental friendliness, shorter reaction time, excellent yields, and simple workup procedure. (C) 2010 Elsevier B.V. All rights reserved.