Abstract: In view of the biological activity of s-triazolo[3,4-b]-1,3,4-thiadiazole fused heterocyclic derivatives, nine novel compounds 3-((4'-chloro)-3'-ethyl-1'-methyl-5'-pyrazolyl)-6-substituted-s-triazolo[3,4-b]-1,3,4-thiadiazoles (4a～g,5,6) were synthesized by condensation of carboxylic acid with 4-amino-3-((4'-chloro)-3'-ethyl-1'-methyl-5'-pyrazolyl)-1,2,4-triazole-5-thione. Their structures were characterized by elemental analysis, ¹H NMR , IR and MS spectroscopy. The preliminary bioassay tests showed that compound 3 exhibited plant growth regulation activity and 4b, 4d and 6 possessed moderate fungicidal activity .

Key words: pyrazolyl-s-triazolo[3,4-b]-1,3,4-thiadiazole, synthesis, bioassay