Synthesis, Anti-inflammatory, Analgesic and Antipyretic Activity of Novel 1,3,5-Trisubstituted Pyrazole Derivatives

A novel series of 1,3,5-trisubstituted pyrazole derivatives were synthesized by the cycloaddition reaction between the electron rich N-substituted aryl hydrazones and nitro-olefins. Different N-substituted aryl hydrazones (1a-j) on reacting with 4-methyl-β-nitrostyrene (2) in ethylene glycol or trifluoroethanol-trifluoro acetic acid mixture (for acid stable hydrazones) at 120 ºC, yielded various 1,3,5-trisubstituted pyrazoles (3a-j). The final products were characterized by spectral analysis using Mass, NMR and IR spectroscopy. All the products were assessed for their anti-inflammatory, analgesic and antipyretic activities on Swiss albino rats. All the compounds (3a-j) exhibited noteworthy defence against inflammation, nociception and hyperthermia. Compounds (3e and 3h) disclosed better antiinflammatory, analgesic and antipyretic activities while compound 3c had highest anti-inflammatory activity compared to the standard nimesulide.