To a solution of tert-butyl {[4-fluoro-5-(2-fluoropyridin-3-yl)-1H-pyrrol-3-yl]methyl}methylcarbamate (200 mg) in tetrahydrofuran (10 mL) was added sodium hydride (60% in oil, 50 mg) at room temperature, and the mixture was stirred for 5 min. 15-Crown-5 (273 mg) was added. Then 1-ethyl-1H-pyrazole-4-sulfonyl chloride (181 mg) was added and the mixture was further stirred for 30 min. The reaction mixture was diluted with water, and extracted with ethyl acetate. The extract was washed with saturated brine, dried over anhydrous magnesium sulfate, and concentrated under reduced pressure. The residue was purified by silica gel column chromatography (eluent: hexane-ethyl acetate=1:1) to give the title compound as a colorless oil (yield 290 mg, 97%).
