A series of 3-alkylthio-5-aryl-1, 2, 4-triazines were synthesized by the condensation of arylglyoxal with S-alkylthiosemicarbazide hydrogen halide in the presence of triethylamine. 3-Substituted 5-aryl-1, 2, 4-triazines were prepared by the nucleophilic substitution of 5-aryl-3-methylsulfonyl-1, 2, 4-triazine with O, N, C-nucleophiles. These compounds were evaluated for antifungal activity against Pyricularia oryzae. The protective effects on rice blast, sheath blight, cucumber powdery mildew were also determined by pot tests. The structure-activity relationship are discussed.
