Synthesis and Antimicrobial Activity of Some New 1,3,4-Thiadiazoles and 1,3,4-Thiadiazines Containing 1,2,4-Triazolo Nucleus

The desired fused ring system 3-(3-chlorophenyl)-6-aryl-5,6-dihydro[1,2,4]triazolo[3,4-b][1,3,4]thiadiazoles 5a–j were synthesized by the reaction of 4-amino-5-(3-chlorophenyl)-4H-1,2,4-triazole-3-thiol and different aryl aldehydes in the presence of catalytic amount of p-TsOH in dry DMF, while 3-(3-chlorophenyl)-6-aryl-7H-[1,2,4]triazolo[3,4- b][1,3,4]thiadiazines 7a–j were synthesized by using 4-amino-5-(3-chlorophenyl)-4H-1,2,4-triazole-3-thiol and different phenacyl bromides in dry methanol. Their IR, 1H NMR, mass spectral data and elemental analyses were in accord with assigned structures. All the newly synthesized compounds were screened for their antimicrobial activity. Some of the compounds exhibited significant inhibition on bacterial and fungal growth as compared to standard drugs.