Design, synthesis, and biological evaluation of novel substituted imidazo[2,1-<i>a</i>]isoindole derivatives as antibacterial agents

<p>An efficient protocol has been developed for the synthesis of fused imidazo[2,1-<i>a</i>]isoindol-5-ones (<b>2a–d</b>) from 2-iodo benzoic acids and <i>N</i>,<i>N</i>-carbonyldiimidazole (CDI) using one-pot Pd-catalyzed C‒C bond coupling. The reaction of imidazo[2,1-<i>a</i>]isoindol-5-one (<b>2a–d</b>) with substituted α-bromo ketones in toluene afforded corresponding imidazo[2,1-<i>a</i>]isoindolium derivatives (<b>3a–i</b>) in good yields. The structures of the title compounds were well established on the basis of infrared (IR), <sup>1</sup>H NMR, carbon-13 nuclear magnetic resonance (<sup>13</sup>C NMR), mass spectral data, and elemental analysis (C, H, and N). <i>In vitro</i> antibacterial results revealed that, the compounds <b>3b</b> and <b>3i</b> were found to possess an excellent broad spectrum of inhibiting potency against all the tested bacterial strains with minimum inhibitory concentration values ranging from 3.125 to 25 µg mL<sup>−1</sup>.</p>