Synthesis and Antibacterial Activity Investigation of New Heterocyclic Compounds from Triazole, Thiadiazole and Oxadiazole Class

Novel derivatives of 1,2,4,-triazole, 1,3,4-thiadiazole and 1,3,4-oxadiazole were synthesized from cyclization of new 1-[4-(phenylsulfonyl)benzoyl]-4-(4-fluorophenyl)-thiosemicarbazide 2 which was obtained by reaction of the 4-(phenylsulfonyl)-benzoic acid hydrazide 1 with 4-fluorophenyl isothiocyanate. The compound 2, in basic medium, gave 1,2,4-triazole-3(4H)-thione 3, whereas in acidic medium 1,3,4-thiadiazol-2-amine 5 was obtained. The synthesis of 1,3,4-oxadiazol-2-amine 6 was carried out by reaction of the same acylthiosemicarbazide 2 with yellow mercuric oxide. Treatment of 1,2,4-triazole 3 with ethyl bromoacetate led to the S-alkylated 1,2,4-triazole derivative 4. The newly synthesized compounds were characterized by elemental analysis and spectral studies (IR, UV-VIS, 1H-NMR, 13C-NMR, MS). All the synthesized compounds have been evaluated in vitro for their antibacterial activity against several strains of pneumococci and different type/reference strains of oral streptococci