[Synthesis and antibacterial activity of 3-(4-piperazin-1-yl-phenyl)-s-triazolo [3,4-b] [1,3,4] thiadiazole hydrochlorides].

To study the synthetic method and antibacterial activity of water-soluble fused heterocyclic compounds containing piperazine group, the nucleophilic substitution of 3-(4-chlorophenyl)-6-substituted-s-triazolo-[3, 4-b] [1, 3, 4] thiadiazoles (2a - n) with piperazine in the presence of phase transfer catalyst TBAI afforded 3-(4-piperazin-1-yl-phenyl)-6-substituted-s-triazolo [3, 4-b] [1, 3, 4] thiadiazole and then followed by acid treatment afforded 3-(4-piperazin-1-yl-phenyl)-6-substituted-s-triazolo [ 3, 4-b] [1, 3, 4] thiadiazole hydrochlorides (3a - n). Twenty-eight new compounds were synthesized and their structures were confirmed by IR, 1H NMR, MS and element analysis. The in vitro antibacterial activities of all newly synthesized compounds were tested against Gram positive bacteria and Gram negative bacteria with the standard 2-fold agar dilution method. Fourteen title compounds exhibited potential antibacterial activities in vitro. The structures of these compounds needed to be further optimized.