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Molecules 2007, 12(7), 1482-1495; doi:10.3390/12071482

New “Green” Approaches to the Synthesis of Pyrazole Derivatives

1,* , 1
1 Dipartimento di Ingegneria dei Materiali e dell’Ambiente, Università degli Studi di Modena e Reggio Emilia, Via Vignolese, 905, 41100 Modena, Italy 2 Dipartimento di Chimica, Università degli Studi di Modena e Reggio Emilia, Via Campi, 183, 41100 Modena, Italy 3 Dipartimento di Scienze Farmaceutiche dell’Università degli Studi di Genova, Viale Benedetto XV, 3, 16132 Genova, Italy
* Author to whom correspondence should be addressed.
Received: 31 May 2007 / Revised: 16 July 2007 / Accepted: 16 July 2007 / Published: 19 July 2007
(This article belongs to the Special Issue Heterocycles)
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A novel approach to the synthesis of pyrazole derivatives from tosylhydrazones of α,β-unsaturated carbonyl compounds possessing a β-hydrogen is proposed, exploiting microwave (MW) activation coupled with solvent free reaction conditions. The cycloaddition was studied on three ketones (trans-4-phenyl-3-buten-2-one, β-ionone and trans-chalcone). The corresponding 3,5-disubstitued-1H-pyrazoles were obtained in high yields and after short reaction times. In order to simplify and point out the green chemistry features of the method, a further improvement was achieved under the same catalytic conditions with a “one pot” synthesis of these heterocyclic compounds, starting directly from their carbonyl precursors via tosylhydrazones generated in situ. For an exhaustive study, the dielectric properties of the solid reaction mixtures were also measured, in order to obtain input data for the numerical simulation of their heating behaviour in the single mode MW cavity which was used for experimental work. In order to supply a valid methodology and tool for measuring the environmental impact, a comparative study between the synthetic route proposed and the classical synthetic route has been carried out.
Keywords: Pyrazole derivatives; solvent free cycloaddition; microwaves Pyrazole derivatives; solvent free cycloaddition; microwaves
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Corradi, A.; Leonelli, C.; Rizzuti, A.; Rosa, R.; Veronesi, P.; Grandi, R.; Baldassari, S.; Villa, C. New “Green” Approaches to the Synthesis of Pyrazole Derivatives. Molecules 2007, 12, 1482-1495.

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