A regioselective synthesis of some new pyrazol-1′-ylpyrazolo[1,5-a]pyrimidines in aqueous medium and their evaluation as antimicrobial agents

An efficient and environmental benign regioselective synthesis of some new pyrazol-1'-ylpyrazolo[1,5-a] pyrimidines (7b-h) has been accomplished via treatment of 3(5)-amino-5(3)-hydrazinopyrazole dihydrochloride (5) with several unsymmetrical 1,3-diketones (6b-h) using water as a solvent without any catalysts or additives. The structure of 7b-h was established on the basis of rigorous analysis of H-1, C-13 NMR, IR spectral data and MS. Eight compounds (7a-h) were screened for their antibacterial activity against two gram-positive and two gram-negative bacteria and compounds (7a, b, d and e) for antifungal activity against four phytopathogenic fungi. Compounds 7c and 7e manifest rather broad antibacterial activity than standard antibiotics. One lead compound, 7a (10 mg/ml and 200 mg/ml) exhibited equipotent or more potent antifungal activity against all tested microorganisms than standard drug. (C) 2011 Elsevier Masson SAS. All rights reserved.