Synthesis and antimicrobial activities of some new [1,2,4] triazolo[3,4-b][1,3,4]thiadiazoles and [1,2,4]triazolo[3,4-b][1,3,4]thiadiazines

Acetic acid hydrazides containing 1,2,4-triazol-3-one ring (4a-d) were synthesized by the reaction of compounds 2a-k with hydrazine hydrate. (5-Mercapto-1,3,4-oxadiazol-2-yl) methyl-2,4- dihydro-3H-1,2,4- triazol-3-one derivatives (5a-d) were obtained from the reaction of compounds 4a-d with carbon disulfide in the presence of KOH. The treatment of compounds 5a-d with hydrazine hydrate led to the conversion of 1,3,4- oxadiazole ring to amino- 1,2,4- triazole ring in compounds 6a-d. A second method involving the reaction of compounds 7a-d with thiocarbohydrazide also gave the same products, 6a-d. The condensation of compounds 6a-d with acetic acid produced 5-alkyl-4-amino- 2-[(6-methyl[ 1,2,4] triazolo[ 3,4- b][ 1,3,4] thiadiazol-3-yl) methyl]-2,4- dihydro-3H-1,2,4- triazol-3- ones (8a-d) while its condensation with carbon disulphide or formic acid afforded 5-alkyl-4-amino- 2-[(6-mercapto[ 1,2,4] triazolo[ 3,4b][ 1,3,4] thiadiazol-3-yl) methyl-(9a-d)and 5-alkyl-4-amino- 2-{([ 1,2,4] triazolo[ 3,4b][ 1,3,4] thiadiazol-3-ylmethyl)}-2,4- dihydro-3H- 1,2,4- triazol-3- ones ( 10a-d), respectively. On the other hand, the synthesis of 5-alkyl-4-amino- 2-[( 6-phenyl-7H-[ 1,2,4] triazolo[ 3,4b][ 1,3,4] thiadiazin-3-yl)methyl]-2,4- dihydro-3H- 1,2,4- triazol-3- ones (11a-d) were performed by the treatment of compounds 6a-d with alpha-bromo acetophenone.