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To optimize the synthetic method and antibacterial activity of fused heterocyclic thiadiazole compounds, cyclocondensation of 2-(4-methoxyphenyl)-5-amino-1,3,4-thiadiazole (2) with alpha-chloro-4-chloro acetophenone (3) resulted in a key intermediate (4), 6 -(4-chlorophenyl)-2-(4-methoxyphenyl)-imidazo-[2,1-b][1,3,4]thiadiazole, which was carried out an nucleophilic substitution with substituted piperazine to give the corresponding free bases of piperazine (5a-5c), then followed by Mannich reaction with heterocyclicamines and formaldehyde to yield the corresponding Mannich bases, (1a-11) as respective hydrochloride salts. The structures were confirmed by IR, 1H NMR, MS and elemental analysis and the antibacterial activities in vitro of fifteen newly synthesized compounds were also tested against Gram positive bacteria and Gram negative bacteria with the standard 2-fold agar dilution method. The antibacterial results showed that the introduction of a polar group resulted in the enhancement of antibacterial activity in vitro. Thus, the structures of these fused compounds could further be investigated.

To study the synthetic method and antibacterial activity of amino-heterocyclic compounds coupled oxime-ether group.The treatment of 4-amino-3-methyl-5-mercapto-s-triazole (3) with beta-chlorophenyl-propanone to form amino-s-triazole sulfanylphenyl-propanone (4) sequentially followed by oximation with hydroxyl-amine to produce the oximes (5) and etherification with various oxadiazole chloromethanes (6a - j) to yield the title compounds (1a - j). 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.Twelve new compounds including two intermediates were synthesized and their structures were confirmed by IR, 1H NMR, MS and elemental analyses. The ten title compounds exhibited the potential antibacterial activities in vitro.Theses compounds should be optimized.

To study on synthesis and antibacterial activity evaluation of polyheterocycles.The condensation of 4-amino-3-pyridin-3-yl-4H-[1,2,4] triazole-5-thiol with 2-chloromethyl-5-substituted phenyl-[1,3,4] oxadiazoles gave the corresponding title heterocycle amines, and the in vitro antibacterial activity was primarily evaluated by the method of cup-plate diffusion solution.Twelve novel compounds were synthesized, and their structures were confirmed by IR, 1H NMR, MS and element analysis. Biological screening results demonstrated that most of the compounds prepared showed good antibacterial activity.Oxadiazoles incorporting pyridyl triazole ring may be a pharmacophor structure in the molecule for developing antibacterial candidate drugs.

Studies on synthesis and antibacterial activity of new heterocycles.The cyclocondensation of [(3-pyridyl)-1,3,4-oxadiazol-2-yl] thio acetic acid with various aroyl hydrazines in the presence of POCl3 and xylene gave the corresponding titled compounds, and the in vitro antibacterial activity was primarily evaluated by the method of cupplate diffusion solution.Sixteen novel titled compounds were synthesized, their structures were confirmed by IR, 1HNMR, MS and elemental analysis. Biological screening results demonstrated that most of the compounds prepared displayed potential antibacterial activity.Oxadiazoles incorporting pyridyl oxadiazole ring may be usefully antibacterial candidate drugs.