To a stirred solution of (E)-(2-chloro-4-(3-(3,5-dichlorophenyl)-4,4,4-trifluorobut-1-en-1-yl)phenyl)methanamine (0.3 g, 0.8 mmol) in CH2Cl2 (10 mL) was added acetic anhydride (0.12 mL, 1.14 mmol), and TEA (0.217 mL, 1.52 mmol), and the resultant reaction mixture was stirred at ambient temperature for 6 h. The reaction mixture was diluted with water and extracted with CH2Cl2. The combined CH2Cl2 layer was washed with brine, dried over Na2SO4, and concentrated under reduced pressure. Purification by flash column chromatography (SiO2, 100-200 mesh; 30-50% EtOAc in hexane) afforded the title compound as a off-white solid (0.2 g, 60%) mp 107-109° C.; 1H NMR (400 MHz, CDCl3) δ 7.37 (m, 3H), 7.28 (m, 4H), 6.60 (d, J=16.0 Hz, 1H), 6.36 (dd, J=16.0, 8.0 Hz, 1H), 5.75 (br s, 1H), 4.46 (d, J=6 Hz, 2H), 4.01 (m, 1H), 2.11 (s, 3H); ESIMS m/z 402.00 ([M+H]+).
