Trametinib Dimethyl sulfoxide(1),a typical anti neo plastic agent drug is used for the treatment of skin cancer. During the laboratory optimization, formation of various impurities wereobserved in the final Trametinib. Origin of these impurities were possible when key starting material 2-fluoro-4-iodo aniline contained2-fluoroaniline, leading to the formation of the des-iodo impurity. Another possibility of des iodo impurity was observed during the nitro reduction step using tin (II) chloride. A cyclic impuritywas also found during nitro reduction step using tin (II) chloride. These impurities were monitored and their structures were tentatively assigned on the basis of their fragmentation patterns in LC-MS. Further, these impurities weresynthesized andcharacterized. We describe here-in, the formation, synthesis and characterization of these impurities.Our study will be of immense help to others to obtain chemically pure Trametinib Dimethyl sulfoxide.
