A METHOD FOR THE SEPARATION OF THE LETROZOLE PRECURSOR 4-'1-(1,2,4-TRIAZOLYL) METHYL!BENZONITRILE FROM ITS 1,3,4-TRIAZOLYL ISOMER

摘要

A chemical method for the separation of letrozole precursor 4-[1-1,2,4-triazolyl)methyl]benzonitrile of formula (I) from the isomeric unwanted byproduct 4-[1-(1,3,4-triazolyl)methyl]benzonitrile of formula (II) of the reaction in which it is produced, which comprises (a) Preparing an isomeric mixtures of the compounds of formula (I) and (II) by conventional methods. (b) Dissolving the resultant crude isomeric mixture in dichloro methane (or) chloroform. (c) Adding 10-14% isopropylalcohol hydrochloride (IPACHI) to the resulting solution. (d) Adding isopropyl ether to precipitate undesired isomer is hydrochloride form. (e) Filtering off the undesired isomer hydrochloride. (f) Distilling off the filtrate completely. (g) Adding dilute sodium hydroxide solution and dichloromethane to the residue to liberate required isomer base of the formula (I). (h) Evaporating the separated dichloromethane layer and charging hexane or petroleum ether. (i) Centrifuging the resultant product of the formula (I) and washing with hexane or petroleum ether.