Base catalyzed one-pot thia-Michael addition-oxidation reaction of hetero-aromatic thiols to 2-aryl-3-nitro-2H-chromenes and their antibacterial evaluation

We report a versatile, Et3N-mediated thia-Michael addition-elimination reaction for producing a series of novel heteroaromatic thiol-based 2H-chromenes in good to excellent yields (59-94%). The protocol involves a one-pot reaction with mild conditions, short reaction period, simple workup procedure, and scalability. The synthesized compounds were screened with different bases and characterized by H-1 NMR, C-13 NMR, and HRMS. The compounds were assessed for their in vitro antibacterial activities against two pathogenic bacterial strains, E. coli and S. aureus. Among all the tested compounds, 17f and 17t exhibited the most excellent potency against both bacterial strains relative to the standard antibiotic, gentamicin, with corresponding MIC values of 12.5 (mu g mL(-1)) and 6.25 (mu g mL(-1)). In the SARs, the compounds 17t and 17f, having -Cl and -Br groups, respectively, showed the highest substantial antibacterial activity. The results revealed a promising lead organosulfur compound for future drug discovery.