Topiroxostat impurity synthesis method

The invention discloses a topiroxostat impurity synthesis method, and belongs to the chemical pharmaceutical technical field. The method comprises the steps: with methyl isonicotinic acid-N-oxide (2) as a starting material, generating 2-cyano-4-pyridine carboxylic acid methyl ester from methyl isonicotinic acid-N-oxide (2) and trimethylsilyl cyanide; carrying out hydrazinolysis of the compound (3) to generate 2-cyano-isoniazid (4); and carrying out ring self-formation of the compound (4) to generate a target 2-(3-(2-amino pyridine-4-yl)-1H-1,2,4-triazole-5-yl)isoniazide (1). The synthesized high-purity topiroxostat impurity can be used as an impurity standard in topiroxostat finished product detection analysis, so as to enhance accurate positioning and qualitation on the impurity in the topiroxostat finished product detection analysis, be conducive to strengthening of the control of the impurity, and improve the quality of the topiroxostat finished product; the method provided by the invention has the advantages of cheap and easily obtained raw materials, and simple operation; the yield of the obtained product is 85%+/-5%, and the HPLC purity is not less than 98%.