An efficient and green protocol for the synthesis of dihydropyrano [2,3-c] pyrazoles in aqueous medium using thiamine hydrochloride as a catalyst

Abstract

A green and expedient approach for the synthesis of dihydropyrano[2,3-c] pyrazoles via four-component reaction of ethyl acetoacetate, hydrazine hydrate, aromatic aldehydes and malononitrile at room temperature under ultrasound irradiation is described. The reaction has been catalyzed by thiamine hydrochloride in aqueous medium. This protocol afforded several advantages such as inexpensive, easily available catalyst, simple operational procedure, excellent yield, use of aqueous medium and ultrasound irradiation that is considered to be relatively eco-friendly.