An impurity was detected in the roflumilast product which was supposed to be N-(3,5-dichloropyridin-4-yl)-4-difluoromethoxy-3-methoxybenzamide. To further verify the impurity structure, this compound was synthesized from 4-difluoromethoxy-3-hydroxybenzaldehyde through O-alkylation, oxidation, chlorination, and amidation reaction and characterized by 1H NMR, 13C NMR, and HPLC–MS. Comparison of the HPLC–MS spectrum of the impurity and the synthesized compound confirmed that they were the same compound. The generation of the impurity was found to be attributed to acetone and iodine in the O-alkylation system.
Research on Chemical Intermediates – Springer Journals
Published: Apr 12, 2013
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