AN EFFICIENT AND GREEN PROTOCOL FOR THE SYNTHESIS OF DIHYDROPYRANO [2,3-C] PYRAZOLES IN AQUEOUS MEDIUM USING THIAMINE HYDROCHLORIDE AS A CATALYST

[摘要] A green and expedient approachfor the synthesis of dihydropyrano[2,3-c] pyrazoles viafour-component reaction of ethyl acetoacetate, hydrazine hydrate, aromaticaldehydes and malononitrile at room temperature under ultrasound irradiationis described. The reaction has been catalyzed by thiamine hydrochloride in aqueousmedium. This protocol afforded several advantages such as inexpensive, easilyavailable catalyst, simple operational procedure, excellent yield, use of aqueousmedium and ultrasound irradiation that is considered to be relatively eco-friendly.

[学科分类] 化学（综合）

[关键词] Multicomponentreaction;Dihydropyrano[2;3-c]pyrazoles;Green chemistry;Aqueous medium;Ultrasound irradiation.