Abstract: Bromination of l-phenyl-3-amino-5-pyrazolone(Ⅰ) in glacial acetic acid gave 1-phenyl-3-amino-4,4-dibromo-5-pyrazolone(Ⅱ).Ⅱ Reacted with a series of substituted hydrazines in hot ethanol to afford l-phenyl-3-amino-5-oxo-4-substituted-hydrazono-pyrazoles(Ⅲ_a-d).Pyrazolo(3,4-e)-1,2,4-triazine(Ⅳ) was formed by cyclization of 4-ethoxycarbonylhydrazone derivative I,in 5% NaOMe solution.By coupling Iwith diazotized aniline or substituted anilines in the presence of pyri-dine, a series of arylhydrazones(Ⅲ) was prepared with a high yield.These compounds were cyclized by diazotization to give the corresponding 2H-2-phenyl-3-oxo-5H-5-arylpyrazolo [3,4-e]-1,2,3,4-tetrazine derivatives(V_a-c).Compound Ⅰreacted with nitrous acid to give 1-phenyl-3-amino-4-ni-troso-5-pyrazolone(Ⅵ).Then Ⅵ was treated with thiosemicarbazide in the boiling pyridine to give 1-phenyl-3-amino-5-oxo-4-thiosemicarbazonopyrazole(Ⅶ).Compound Ⅶ was cyclized under a alkaline condition to give pyrazolo[3,4-e]-l,2,4-triazine(Ⅷ).

Key words: Synthesis, Pyrazolo[3,4-e]-1,2,4-triazine, Pyrazolo[3,4-e]-1,2,4-triazine