Trifluoroacetic acid → (E)-5-(3-(3,5-dichloro-4-fluorophenyl)-4,4,4-trifluorobut-1-en-1-yl)-1H-indole

To a stirred solution of (E)-tert-butyl 5-(3-(3,5-dichloro-4-fluorophenyl)-4,4,4-trifluorobut-1-enyl)-1H-indole-1-carboxylate (0.2 g, 0.40 mmol) in DCM (10.0 mL) was added TFA (70 mg, 0.61 mmol) and the reaction was stirred at RT for 2 h. The reaction mixture was diluted with DCM and washed with saturated NaHCO3 solution, water and brine solution. The separated DCM layer was dried over anhydrous Na2SO4 and concentrated under reduced pressure to afford the title compound as a light brown solid (0.2 g, 97%): mp 132.9-138.8° C.; 1H NMR (400 MHz, CDCl3) δ 11.19 (br, 1H), 8.20 (d, J=8.0 Hz, 1H), 7.60 (m, 2H), 7.39 (m, 3H), 6.69 (d, J=16.0 Hz, 1H), 6.55 (d, J=10.5 Hz, 1H), 6.36 (dd, J=16.0, 8.0 Hz, 1H), 4.82 (m, 1H); ESIMS m/z 387.98 ([M+H]+).