An Investigation into the Formation of Impurity B during the Optimization of Naratriptan Hydrochloride

During the process development of naratriptan hydrochloride we have made an unusual observation about the enhanced levels of intermediate 3 as an impurity (impurity B) in the final stage. Detailed investigation has led to the conclusion that impurity B is not only a carried over but also formed via acid catalyzed dehydration of yet another process related impurity. The present work details a report of the journey towards the development of an efficient process for the commercial production of naratriptan hydrochloride substantially free from the impurity B.