Synthesis, characterization and biological evaluation of 4-{1-aza-2-[(aryl) amino]}-3-methyl-2-pyrazolin-5-ones derivatives

A series of substituted 4-{1-aza-2-[(aryl) amino)]}-3-methyl-2-pyrazolin-5-ones has been synthesized and evaluated for their biological activity. The title compounds (4a-l) were prepared by the diazotization of substituted anilines (1a-l) to form substituted phenyl hydrazine derivatives (2a-l) which synthesized substituted 4-{1-aza-2-[(aryl) amino)]}-3-methyl-2-pyrazolin-5-ones (4a-l) by Michael addition reaction, which is a nucleophilic addition of enolate anion to the carbon-carbon double bond of a α-unsaturated carboxylic acid derivatives. Twelve different pyrazolinone derivatives (4a to 4l) were synthesized. Structural assignments of these compounds have been made by elemental analysis, FTIR, ¹HNMR and Mass spectral data and the purity of the compounds was determined by TLC. The antimicrobial activity of the newly Synthesized heterocyclic compounds were evaluated against Gram-positive, Gram-negative bacteria and fungi. Most of the compounds showed a moderate degree of potent antimicrobial activity. While analgesic activities were tested via both hot plate and acetic acid induced writhing methods. The study concluded that the compound 4b and4f were found to exhibit significant analgesic activity when compared to Diclofenac as standard drug while other derivatives exhibit moderate to good analgesic activity.