Regorafenib-N-Oxide

Regorafenib-N-Oxide is a structurally defined oxidation derivative of regorafenib, featuring an N-oxide moiety on the 1H-benzimidazole ring. Its core architecture includes a 4-chloro-6-(5-fluoropyridin-2-yl)pyrimidin-4-yl group linked to a 2-(3-chloro-4-fluorophenyl)-1H-benzimidazole-2-yl N-oxide. The molecule incorporates multiple heterocyclic systems, including a pyrazine ring fused to the benzimidazole, along with trifluoromethyl and chloro substituents. This impurity arises via oxidative degradation pathways during API synthesis or storage. It serves as a specific oxidative degradation byproduct used as an HPLC reference standard for impurity profiling in regorafenib formulations.