To a solution of 4-(2-fluoro-4-trimethylsilanylphenylamino)-indazole-1,5-dicarboxylic acid di-tert-butyl ester (1.07 g, 2.14 mmol) in DCM (10 mL) at 0° C. was added iodine monochloride as a solution in DCM (4.2 mL, 1N, 4.2 mmol). The reaction mixture was stirred at 0° C. for 20 minutes then diluted with saturated aqueous sodium thiosulfate solution (10 mL) and extracted with DCM (2×10 mL). The combined organic extracts were washed with brine (20 mL), dried (MgSO4) and concentrated in vacuo. The resultant residue was subjected to flash chromatography (Si—PPC, gradient 0-100% DCM in cyclohexane) to yield the title compound as a pale brown solid (611 mg, 52%). LCMS (Method B): RT=5.48 min, [M+H]+=554.
