To 2-methylindazole-3-carboxylic acid (650 mg, 3.69 mmol) and DMF (29.0 μl, 0.37 mmol) was added benzene (20 ml). Under stirring at room temperature, oxalyl chloride (0.39 ml, 4.43 mmol) was added dropwise to the resulting mixture. After completion of the dropwise addition, the reaction mixture was stirred for further 1 hour at room temperature. A solution of ethyl (4-amino-5-chloro-2-fluorophenyl)acetate (855 mg, 3.69 mmol) and triethylamine (3.09 ml, 22.1 mmol) in benzene (3.0 ml), which had been prepared in advance, was added dropwise to the reaction mixture, and the mixture was heated under reflux for 16 hours. The reaction mixture was then cooled to room temperature, followed by extraction with ethyl acetate. The extract was washed with saturated brine, dried over anhydrous sodium sulfate, and distilled under reduced pressure to remove the solvent. The residue was purified by chromatography on a silica gel column, whereby from n-hexane-ethyl acetate (5:1, v/v) eluate fractions, ethyl (5-chloro-2-fluoro-4-((2-methyl-3-indazolylcarbonyl)amino)phenyl)acetate (390 mg, 27%) was obtained as a pale yellow solid.
