Original Articles
G. B. Narashimha Reddy, A. Nar
Abstract
A detail study was undertaken to investigate origin of Roflumilast drug substance related impurities. These impurities were synthetically prepared and characterized by IR, NMR and Mass, in order to have proper process control. These impurities are N-(3,5-Dichloropyridin-4-yl)-3,4-bis(difluoromethoxy)benzamide (Roflumilast impurity-I), 4-(Cyclopropylmethoxy)-N-(3,5-dichloropyridin-4-yl)-3-(difluoromethoxy)benzamide (Roflumilast impurity-II), 3,4-Bis(cyclopropylmethoxy)-N-(3,5-dichloropyridin-4-yl)benzamide (Roflumilast impurity-III), 3- Cyclobutyl-N-(3,5-dichloropyridin-4-yl)-4-(difluoromethoxy)benzamide (Roflumilast impurity-IV), 3-(But-3-en-1- yloxy)-N-(3,5-dichloropyridin-4-yl)-4-(difluoromethoxy)benzamide (Roflumilast impurity-V), 3- (Cyclopropylmethoxy)-4-(difluoromethoxy)-N-(pyridin-4-yl)benzamide (Roflumilast impurity-VI), N-(3- Chloropyridin-4-yl)-3-(cyclopropylmethoxy)-4-(difluoromethoxy)benzamide (Roflumilast impurity-VII) and 3,5- Dichloro-4-[3-(cyclopropylmethoxy)-4-(difluoromethoxy)benzamido]pyridine-1-oxide (Roflumilast impurity -VIII).