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

ABSTRACT

An efficient protocol has been developed for the synthesis of fused imidazo[2,1-a]isoindol-5-ones (2a–d) from 2-iodo benzoic acids and N,N-carbonyldiimidazole (CDI) using one-pot Pd-catalyzed C‒C bond coupling. The reaction of imidazo[2,1-a]isoindol-5-one (2a–d) with substituted α-bromo ketones in toluene afforded corresponding imidazo[2,1-a]isoindolium derivatives (3a–i) in good yields. The structures of the title compounds were well established on the basis of infrared (IR), ¹H NMR, carbon-13 nuclear magnetic resonance (¹³C NMR), mass spectral data, and elemental analysis (C, H, and N). In vitro antibacterial results revealed that, the compounds 3b and 3i 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⁻¹.

GRAPHICAL ABSTRACT

KEYWORDS:

• Antibacterial activity
• imidazo[2,1-a]isoindoles
• imidazolium salts
• Pd-coupling

Acknowledgments

Narsimha thanks CSIR, New Delhi, for the award of senior research fellowship. The authors are thankful to the Head, Department of Bio-Technology, Kakatiya University, Warangal, for providing data of biological activity.