Fifteen novel 5,7-dimethyl-1,2,4-triazolo[1,5-a] pyrimidine-2-oxoacetohydrazone derivatives and ten novel (R)-5,7-dimethyl-1,2,4-triazolo[1,5-a] pyrimidine-2-oxo (α-methyl) acetohydrazone derivatives were designed and synthesized by using 5,7-dimethyl-1,2,4-triazolo[1,5-a] pyrimidine-2-methylthioether as the starting material. All synthesized compounds were confirmed by elemental analysis, MS and 1H NMR. The preliminary bioassay indicates that some of them display good herbicidal and fungicidal activities. Thos...