An Efficient Four Component Domino Synthesis of Pyrazolopyranopyrimidines using Recyclable Choline Chloride:Urea Deep Eutectic Solvent

An efficient synthesis of pyrazolopyranopyrimidines was achieved by four component domino reaction of aldehydes, barbituric acid, hydrazine hydrate, and ethyl acetoacetate using biodegradable and recyclable choline chloride:urea as deep eutectic solvent. The reaction proceeds rapidly and affords the corresponding diverse tricyclic fused pyrazolopyranopyrimidines with a good to excellent yield. The protocol has the advantage of easy workup, high yields, and an environmentally benign methodology compared with other reported methods. The simplicity of this method makes it an interesting alternative to other approaches.