3-Alkyl/aryl-4-amino-5-mercapto-1, 2, 4-triazoles (2) were condensed with 2-phenyl-1, 2, 3-triazole-4-carboxyl acid(1) in the presence of phosphorus oxychloride to afford fifteen novel 3-lkyl/aryl-6-(2'-phenyl-1', 2', 3'-triazole-4'-yl)-s- triazolo[3, 4-b]-1, 3, 4-thiadiazoles (3a～o).

Key words: HETEROCYCLIC COMPOUNDS, PYRRODIAZOLE P, ARYL GROUP, CARBOXYLIC ACID, PYRRODIAZOLE P, ORGANIC SYNTHESIS, THIADIAZOLE P, PHENYL GROUP, MERCAPTO COMPOUNDS, CONDENSATION REACTION