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.
Keywords: Spiroheterocycles, catalyst-free, pyranopyrazole, environmentally-friendly, water.
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