| 摘要 |
The present invention relates to a process for the preparation of 4-[1-(4-cyano phenyl)-1-(1,2,4-triazol-1-yl)methyl]benzonitrile (letrozole), substantially free from its isomeric impurity. The preparation involves reaction of 4-[1-(1H-1,2,4-triazol-1-yl)methylene benzonitrile with 4-fluorobenzonitrile in the presence of an organic solvent and a silicon amine. The present invention also relates to a process for the preparation of 4-[1-(1H-1,2,4-triazol-1-yl)methylene benzonitrile which involves: (a) the reaction of a 4-halomethyl benzonitrile with 1,2,4-triazole in the presence of cesium carbonate and an organic solvent to obtain a reaction mass comprising 4-[1-(1,2,4-triazole-1-yl)methyl]benzonitrile of formula II; and (b) precipitation of 4-[1-(1,2,4-triazole-1-yl)methyl]benzonitrile (II) from the reaction mass using a suitable organic solvent.
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