A 50 mL round-bottomed flask was charged with N-(1H-indazol-4-yl)-3-(2-methyl-6-(methylthio)pyrimidin-4-yl)quinoxalin-2-amine (150 mg, 0.375 mmol) in DCM-DMF(5:1, 6 mL). mCPBA (130 mg, 0.751 mmol, Aldrich) was added to this solution at 0° C., the mixture was stirred at 0° C. for 2 h, then warmed to room temperature and diluted with saturated NaHCO3. The aqueous layer was extracted with DCM (3×), and the combined organic extracts were washed with brine, dried over MgSO4, and concentrated in vacuo. The crude material was purified by chromatography through a Redi-Sep pre-packed silica gel column (40 g) eluting with a gradient of 2% to 10% 2M NH3.MeOH in DCM to give N-(1H-indazol-4-yl)-3-(2-methyl-6-(methylsulfinyl)pyrimidin-4-yl)quinoxalin-2-amine (36 mg, 0.087 mmol, 23% yield) as an orange solid. m/z (ESI, +ve ion) 416 (M+H)+.
