Microwave-assisted synthesis of pyrido[1,2-a]benzimidazole derivatives of β-aryloxyquinoline and their antimicrobial and antituberculosis activities

A new series containing pyrido[1,2-a]benzimidazole derivatives of beta-aryloxyquinoline has been synthesized via base catalyzed microwave-assisted multi-component cyclocondensation reaction. This methodology allowed us to achieve the desired products in good yields in very short time with the use of 10 mol% NaOH as a non-hazardous organic base. The chemical structures of compounds 6a-x were elucidated by H-1 NMR, C-13 NMR, FT-IR, elemental analysis, and mass spectral data. The titled derivatives were tested against a panel of pathogenic strains of bacteria and fungi for antimicrobial activity and against Mycobacterium tuberculosis H37Rv for their antitubercular activity. The structural activity relationship study revealed that antimicrobial and antitubercular potency of the title compounds depends not only on the bicyclic heteroaromatic pharmacophore appended through ether linked aryl ring but also on the nature of the peripheral substituents and may also upon their spatial relationship and positional changes.