Synthesis, characterization and antimicrobial evaluation of some novel 1,2,4-triazolo[3,4-b][1,3,4]thiadiazine bearing substituted phenylquinolin-2-one moiety

Abstract

Pathogenic microbes have mutated and developed resistance to the latest range of antibiotics, which has kept synthetic chemist hunting for better and least toxic antimicrobial agents. Cyclocondensation of substituted anilines with 3-phenyl-2-propenoic acid yielded Phenyl-(substituted)-quinolin-2-one derivatives (1a–1t). In the next step phenylquinolin-2-one acetic acid derivatives (2a–2t) were prepared by the treatment of (1a–1t) with chloroacetic acid. Further (2a–2t) derivatives were reacted with thiocarbohydrazide to obtain a series of 4-amino-5-sulfanyl-4,5-dihydro-1,2,4-triazolo-4-pheny-(substituted)-quinolin-2-one derivatives (3a–3t). Then condensation of (3a–3t) with phenacyl bromide provided series of fused heterocyclic derivatives of 4-phenyl-1-({6-phenyl-7H-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazin-3-yl}methyl)-(substituted)-1,2-dihydro quinolin-2-one (4a–4t). Structures of these newly synthesized derivatives were established by elemental analysis, FT-IR, 1H NMR and Mass spectroscopy. Final derivatives (4a–4t) were screened for their in vitro antibacterial and antifungal activities against the standard drugs Ampicillin and Fluconazole respectively. The compounds 4d, 4g and 4j showed potent activity against all the studied microbes. Particularly compounds substituted with halogen groups at para position of phenylquinoline ring exhibited significant antimicrobial activity against studied microbes. Keywords: Antimicrobial, Cyclocondensation, Phenylquinoline, Triazolothiadiazine