Synthesis and Biological Screening of New 2-(5-Aryl-1-phenyl-1<i>H</i>-pyrazol-3-yl)-4-aryl Thiazole Derivatives as Potential Antimicrobial Agents

Abstract

A new series of 2-(5-aryl-1-phenyl-1<i>H</i>-pyrazol-3-yl)-4-aryl thiazoles (<b>10a</b>-<b>ab</b>) have been synthesized by a cyclocondensation reaction of 5-aryl-1-phenyl-1<i>H</i>-pyrazole-3-carbothioamide (<b>7a</b>-<b>d</b>) with substituted phenacyl bromide (<b>8a</b>-<b>f</b>). The structure of newly synthesized 2-(5-aryl-1-phenyl-1<i>H</i>-pyrazol-3-yl)-4-aryl thiazole (<b>10a</b>-<b>ab</b>) derivatives was characterized by spectroscopic analysis. The compounds <b>10a</b>-<b>ab</b> were evaluated for <i>in vitro</i> antibacterial activity against <i>Escherichia coli</i> (NCIM 2574), <i>Proteus mirabilis</i> (NCIM 2388), <i>Bacillus subtilis</i> (NCIM 2063), <i>Staphylococcus aureus</i> (NCIM 2178), and <i>in vitro</i> antifungal activity against <i>Aspergillus niger</i> (ATCC 504) and <i>Candida albicans</i> (NCIM 3100). Among the twenty-eight pyrazolyl<b>-</b>thiazole derivatives, six compounds, <b>10g</b>, <b>10h</b>, <b>10i</b>, <b>10j</b>, <b>10o</b>, and <b>10t</b>, showed good activity against <i>P. mirabilis</i>; four compounds <b>10q</b>, <b>10u</b>, <b>10y</b>, and <b>10z</b> showed good activity against <i>S. aureus</i>; and twenty-four derivatives showed good antifungal activity against <i>A. niger</i>. Compounds <b>10g</b>, <b>10q</b>, <b>10r</b>, <b>10s</b>, and <b>10ab</b> showed comparable activity with respect to the reference drug Ravuconazole. Thus, the significant antimicrobial activity of 2-(5-aryl-1-phenyl-1<i>H</i>-pyrazol-3-yl)-4-aryl thiazole (<b>10a</b>-<b>ab</b>) derivatives prompted that these scaffolds could assist in the development of lead compounds to treat microbial infections.