Understading and controlling the formation of process related impurity during development of eszopiclone

Eszopiclone (5) belongs to a novel class of non-benzodiazepine hypnotics which is structurally unrelated to existing hypnotics. During commercialization, upto 3.85% of a unknown impurity was observed in penultimate step. This was identified as a N-methyl piperazine related impurity of Eszopiclone. Subsequent investigation and design of experiments led to the identification of factors responsible for the formation of this impurity. Implementation of knowledge gained from the reproducible experiments enabled the suppression of this impurity to the acceptable levels. In this manuscript different parameters for process developments such as optimization of critical parameters to control the new impurity, identification, synthesis origin and control of impurity of a scalable process for Eszopiclone are discussed.

Author(s): Neelakandan K., Anil B. Chavan, N. Santosha, B. Prabhakaran and N. Santhi

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