SYNTHESIS AND ANTIBACTERIAL SCREENING OF SCHIFF BASES DERIVED FROM 3-(5-BROMOTHIOPHEN-2-YL)-1-(4-CHLOROPHENYL)-1H-PYRAZOLE-4-CARBALDEHYDE

A series of new Schiff bases were synthesized by condensation of 3-(5-bromothiophen-2-yl)-1-(4-chlorophenyl)-1H-pyrazole-4-carbaldehyde with different aromatic aldehydes. The 3-(5-bromothiophen-2-yl)-1-(4-chlorophenyl)-1H-pyrazole-4-carbaldehyde was prepared from 1-(1-(5-bromothiophen-2-yl)ethylidene)-2-(4-chlorophenyl)hydrazine by the Vilsmeier Haack reaction. The 1-(1-(5-bromothiophen-2-yl)ethylidene)-2-(4-chlorophenyl) hydrazine was prepared by the condensation reaction of 2-acetyl-5-bromothiophene with 4-chlorophynylhydrazine hydrochloride. The structures of newly synthesized compounds were elucidated by NMR, IR, and Mass spectral – data. Prepared Schiff bases were evaluated for antibacterial activity against four organisms: Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and Klebsiella pneumoniae using streptomycin as a standard drug. Agar well-diffusion method was followed to determine the antimicrobial activity. All prepared Schiff bases showed poor to good activity against test organisms. Based on the zone of inhibition results, it is observed that the newly prepared Schiff bases showed better activity against Klebsiella pneumoniae than Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa. Schiff base 4c showed good activity against Pseudomonas aeruginosa, Schiff base 4l showed good activity against Staphylococcus aureus and all the Schiff bases 4a-4l except 4c showed good activities against Klebsiella pneumoniae.