N-Trifluoroacetylated pyrazolines: Synthesis, characterization and antimicrobial studies

Abstract

A series of N-trifluoroacetyl-2-pyrazolines have been synthesized via cyclization of chalcones in the presence of trifluoroacetic acid and hydrazine as a base. The method used for the preparation of pyrazolines was found to be an efficient one as all of the compounds were obtained in good yield (up to 79%). Various spectroscopic techniques established the structures and additionally corroborated the compounds 2a and 2e by single crystal X-ray. Newly synthesized pyrazolines were investigated for their potential as antimicrobial agents. Compound 2a displayed promising antimicrobial activity against pathogenic Escherichia coli and Pseudomonas aeruginosa. Furthermore, the mechanism of the antimicrobial activity of 2a was demonstrated with the help of scanning electron microscopy (SEM), which revealed complete damage of the bacterial cell membrane, providing dead cell debris in the milieu. The minimum inhibitory concentration (MIC) observed was 79 and 90 µM against E. coli and P. aeruginosa, respectively. Hence, these compounds might be significantly useful in antimicrobial drug development.