4-chlorobutanoyl chloride (670 mg, 4.76 mmol) was added dropwise to a 0° C. solution of ethyl 6-amino-5-bromo-2-(4-fluorophenyl)benzofuran-3-carboxylate and Et3N (1.0 mL) in CH2Cl2 (10 mL) under N2 atmosphere. The resulting reaction was allowed to stir at room temperature for 16 hours, then the reaction mixture was concentrated in vacuo. The resulting resulting residue was dissolved in CH3CN (10 mL), and then K2CO3 (658 mg, 4.76 mmol) and KI (263 mg, 1.59 mmol) was added and the mixture was heated to reflux and allowed to stir at this temperature for 16 hours. After being cooled to room temperature, the mixture was diluted with water and extracted with EtOAc. The organic extract was washed with brine, dried over Na2SO4, filtered and concentrated in vacuo. The residue obtained was purified using column chromatography (eluted with petroleum ether:EtOAc=2:1) to provide ethyl 5-bromo-2-(4-fluorophenyl)-6-(2-oxopyrrolidin-1-yl)benzofuran-3-carboxylate (280 mg, yield: 40%). 1H-NMR (CDCl3, 400 MHz) δ 8.32 (s, 1H), 8.04˜8.07 (m, 2H), 7.48 (s, 1H), 7.17˜7.21 (m, 2H), 4.42˜4.43 (m, 2H), 3.82˜3.86 (m, 2H), 2.61˜2.65 (m, 2H), 2.27˜2.31 (m, 2H), 1.40˜1.44 (m, 3H). MS (M+H)+: 446/448.
