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 CH2Cl2 (10.0 mL) was added TFA (70 mg, 0.61 mmol) and the reaction was stirred at ambient temperature for 2 h. The reaction mixture was diluted with CH2Cl2 and washed with saturated NaHCO3 solution, water and brine solution. The separated CH2Cl2 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]+).