1,3-Di-n-butylimidazolium tribromide [BBim]Br3: An efficient recyclable catalyst mediated synthesis of N-substituted azepines and their biological evaluation-interaction study with human serum albumin

A majority of previously reported methods suffer from insufficient yields as well as more complicated experimental procedures, a smaller amount of isolated yields involving time-consuming and tiresome work-up with the use of metal catalyst and restricted scope of substrates. To overcome these issues, an environmentally benign, ionic liquid endorsed multi-component protocol to N-substituted azepines has been exploited by means of coupling aromatic amines, dimethyl/diethyl acetylene dicarboxylate, 2,5-dimethoxytetrahydrofuran using 1,3-Di-n-butylimidazolium tribromide [BBim]Br3. The catalyst can be recycled and reused for subsequent reactions. The reactivated ionic liquid could be further reused twice as an accelerator All the synthesized compounds were further screened for their antimicrobial properties against three gram positive, four gram negative, and five fungal strains with chloromycin, norflaxacin, and fluconazole as reference drugs. Most of the tested compounds presented significant potency, especially, compound 4e displayed significant antibacterial activity (MIC=1-16μg/mL) whereas compound 4k showed momentous antifungal efficacy (MIC=2-32μg/mL). In addition binding behavior of compound 4e was investigated by binding study between calf thymus DNA and compound 4e by UV-Visible absorption spectroscopy and further research about HSA interactions were carried out. The observed wavelength showed a constancy thus revealing the occurrence of non-covalent π-π stacking interactions of compound 4e and HSA.