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Zwitterionic sulfamic acid functionalized nanoclay (MMT-ZSA) was prepared with montmorillonite K10 as template, 3- aminopropyltriethoxysilane as linker and chlorosulfonic acid as a SO 3 H source. The physical and chemical properties of zwitterionic nanoclay were characterized by the following instrumental techniques: FT-IR spectroscopy, elemental analysis, TGA, DTA, SEM, XRD, elemental analysis and Hammett acidity function techniques. The catalytic activity of MMT-ZSA was investigated in the synthesis of dihydropyrano[2,3-c]pyrazoles and spiro[indoline-3,4 ´ -pyrano[2,3-c]pyrazole] derivatives via the multicomponent reaction between hydrazine hydrate (or phenyl hydrazine), malononitrile, β -keto ester and carbonyl compounds (1,2-di ketones and benzaldehyde derivatives) under solvent-free conditions. Using this synthetic method, the title compounds were prepared in high to excellent yields and short reaction times. Other remarkable features include heterogeneous reaction conditions, a much milder procedure, and a wide range of functional group tolerance, high reaction rates, absence of any tedious workup or purification, and reusability of the catalyst. This synthetic protocol also avoids hazardous reagents/solvents and is thus an eco-friendly, alternative approach to the existing methods. |
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