The invention provides a preparation method of
anastrozole. The preparation method comprises the following steps that 1, 5-bromomethyl-a,a,a',a'-tetramethyl-1,3-
xylylene cyanide and 4-amino-1,2,4-
triazole are taken as raw materials to react in an
organic solvent, and
crystallization is conducted to obtain an intermediate I, that is, a,a,a',a'-tetramethyl-5-[(4-amino-1,2,4-triazol)-
methylene]-1,3-
xylylene cyanide bromide; 2, the intermediate I is dissolved into a
solvent, a little amount of water, acid and a
metal catalyst are added,
sodium azide is added in batches in a
reflux state, immediate
filtration is conducted after a complete reaction, a mother solution is concentrated until the volume of the solution is 0.25-0.75 times of the original volume of the mother solution, cooling
crystallization is conducted, solids are filtered and subjected to
PH regulation and extraction, and concentration is conducted to obtain a crude
anastrozole product; 3, the crude
anastrozole product is dissolved into an
alcohol solvent, decoloring and cooling
crystallization are conducted, and the fine anastrozole product is obtained. According to the preparation method, iso-anastrozole impurities influencing the medicinal
efficacy are prevented from being generated from the source, no iso-anastrozole is detected out, the remaining single
impurity content is less than 0.05%, and the remaining total
impurity content is less than 0.2%.