To a mixture of 5-bromo-3-(4-fluoro-1H-indol-2-yl)pyridin-2-ol (1.0 g, 3.26 mmol), DIPEA (1.26 g, 9.77 mmol) and DMAP (80 mg, 0.65 mmol) in 15 mL of DCM was added Tf2O (1.84 g, 6.51 mmol) at 0 dropwise. After stirring at room temperature for 3 hours, the mixture was suspended in water and extracted with DCM. Then the combined organic phase was washed with brine, dried over sodium sulfate and concentrated. After column chromatography (PE:EA=20:1), 5-bromo-3-(4-fluoro-1H-indol-2-yl)pyridin-2-yl trifluoromethanesulfonate (1.0 g, yield: 52%) was obtained. 1H-NMR (DMSO-d6, 400 MHz) δ 12.28 (s, 1H), 8.81 (s, 1H), 8.60 (s, 1H), 7.32 (d, J=8.40 Hz, 1H), 7.18˜7.22 (m, 1H), 7.05 (s, 1H), 6.84˜6.87 (m, 1H). MS (M+H)+: 439/441.
