Pure intermediate for preparing letrozole

摘要

The present invention relates to an improved process for the preparation of Letrozole (I) and its synthetic intermediate 4-[(1-(1,2,4-triazolyl)methyl]benzonitrile (III). In particular, it relates to a process to prepare Letrozole and its intermediate (III) substantially free from regioisomeric impurities. The present invention further relates to acid addition salts of 4-[(1-(1,2,4-triazolyl)methyl]benzonitrile (III) such as the oxalate salt, and also to Letrozole (I), the intermediate (III) and salts thereof preparable by the processes of the present invention.