In Vitro Antibacterial Evaluation of Synthesized 1,2,4-Triazolo[5,1-b]1,3,4-thiadiazole Derivatives

Because of the broad spectrum of biological activities and synthetic utilities of triazole and thiadiazole derivatives, we synthesized some new 2-aryl-[1,2,4]triazolo[5,1-b][1,3,4]thiadiazole-6(5H)-thione derivatives (4a-e) and evaluated them for in vitro antibacterial activity by using by agar diffusion method. The 1,2,4-triazolo-thiadiazole derivatives were synthesized by the reaction of different aromatic aldehydes with thiosemicarbazide in presence of ethanol to form 2-arylidene hydrazine carbothioamide derivatives (1a-e). Compounds 1a-e got cyclized when reacted with sodium acetate and bromine in glacial acetic acid to form 5-aryl-1,3,4-thiadiazol-2-amine derivatives (2a-e). Compounds 2a-e were reacted with ammonium thiocyanide in presence of water to form 1-(5-aryl1,3,4-thiadiazol-2-yl)urea derivatives (3a-e). Compounds 3a-e were reacted with thionyl chloride in the presence of pyridine to form title compounds 4a-e. Spectral analyses, including IR,¹H-NMR, and mass spectrometry, were used to characterize the synthesized compounds. The result showed that all the title compounds exhibited antibacterial activity. Compounds 4b and 4e were more active against all the bacterial strains. Compound 4a is the least effective against P. aeruginosa. Compound 4c is least effective against E. coli and compound 4d is least effective against S. aureus. Antibacterial studies were compared to the standard drug Ciprofloxacin.