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E-mail: bandgar_bp@yahoo.comReceived August 26, 2011, Accepted September 11, 2011A series of pyranopyrazoles, was efficiently synthesized via one-pot, four component reaction of ethylacetoacetate, hydrazine hydrate, aldehydes and malononitrile in the presence of catalytic amount silicotungsticacid under solvent free condition. NOE experiments confirmed that the product exist exclusively in the 2Hform. The present protocol offers the advantages of clean reaction, short reaction time, high yield, easypurification and economic availability of the catalyst.Key Words : Pyranopyrazoles, Multicomponent, Heteropolyacid, Solvent-free, NOEIntroductionAn increase in regulatory restrictions on the use, manu-facture and disposal of organic solvents has focused atten-tion on the development of non-hazardous alternatives suchas solvent-free syntheses, multicomponent reactions andreusable heterogeneous catalysts for the sustainable develop-ment of chemical enterprise. These organic reactions possessadvantages over traditional reactions in organic solvents.For example, solvent-free, multicomponent reactions withreusable heterogeneous catalysts reduce the consumption ofenvironmentally hazardous solvents and utilize scaled-downreaction vessels. In the recent years, the use of solid acids asheterogeneous catalyst has received considerable attention indifferent areas of organic synthesis.

Rapid One-pot, Four Component Synthesis of Pyranopyrazoles Using Heteropolyacid Under Solvent-free Condition