Green Access to Multi-Component Synthesis of Spiropyranopyrazoles

A catalyst-free multi-component synthesis of spiro[indoline-3,4’-pyrano[2,3-c]pyrazoles] is reported from in situ formed pyrazolone by exothermic reaction of ethyl acetoacetate with hydrazine hydrate, isatin and malononitrile in water at room temperature. A suggested mechanistic approach was supported by semi-empirical calculations. The transformation is carried out in water alone and thus achieved the highest level of green chemistry. Simple reaction conditions, easy work-up procedure and isolation of products are the auxiliary advantages of present protocol.