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Synlett 2007(10): 1600-1604  
DOI: 10.1055/s-2007-982545
LETTER
© Georg Thieme Verlag Stuttgart · New York

Synthesis of Pyrazoles by a One-Pot Tandem Cyclization-Dehydrogenation Approach on Pd/C/K-10 Catalyst

Shainaz M. Landge, Allison Schmidt, Verona Outerbridge, Béla Török*
Department of Chemistry, University of Massachusetts Boston, 100 Morrissey Blvd., Boston, MA 02125, USA
Fax: +1(617)2876030; e-Mail: bela.torok@umb.edu;
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Publikationsverlauf

Received 22 March 2007
Publikationsdatum:
06. Juni 2007 (online)

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Abstract

A novel one-pot synthesis of substituted pyrazoles from chalcones and hydrazines via a tandem cyclization-dehydro­genation approach is described. This process is based on the use of a bifunctional noble-metal/solid-acid catalyst, Pd/C/K-10 montmorillonite and microwave irradiation under solvent-free conditions. The cyclization of chalcones with hydrazines readily takes place on the strong solid acid while the presence of the metal ensures the ­formation of the aromatic product through dehydrogenation. The ­reactions are complete in 30 minutes providing good yields and high selectivities.

Key words

chalcones - hydrazines - bifunctional catalysis - microwave heating - pyrazoles

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