Eleven novel 2-alkylthio-5-(5,7-dimethyl-1,2,4-triazolo[1,5-a]pyrimidine-5-yl)-1,3,4-oxadiazole derivatives (5) and six novel 2-alkylthio-5-(5,7-dimethyl-1,2,4-triazolo[1,5-a]pyrimidine-5-yl)-1,3,4-thia- diazole derivatives (8) have been designed and synthesized by using 5-amino-3-ethoxycarbonyl-1H-1,2,4- tri-azole as a starting material. All compounds synthesized were confirmed by ¹H NMR, MS spectra and elemental analyses. Preliminary bioassay indicates that some compounds display herbicidal ac-tivity and excellent fungicidal activity to some extent, and among them the compounds 5k and 8f b> exhibit higher than 90% inhibition effect against Rhizoctonia solani in dosage of 50 mg/L.

Key words: 1,3,4-oxadiazole, synthesis, 1,3,4-thiadiazole, linked biheterocycle, biological activity, 1,2,4-triazolo[1,5-a]pyrimidine