To a solution of (4-fluoro-3-isopropoxyphenyl)(3-fluoro-5-(1,1,2,2-tetrafluoroethoxy)phenyl)methanamine (2.8 g, 7.1 mmol) in CH2Cl2 (30 mL) at 0° C. was added acetic formic anhydride (2.8 mL, formed by heating a 2:1 v/v ratio of acetic anhydride and formic acid at 60° C. for 2 h). The reaction mixture was allowed to warm to room temperature and stirred for 0.5 h. The reaction mixture was concentrated under reduced pressure and the residue was purified by ISCO (120 g silica gel column, 0 to 60% EtOAc/hexane over 60 min gradient) to give N-((4-fluoro-3-isopropoxyphenyl)(3-fluoro-5-(1,1,2,2-tetrafluoroethoxy)phenyl)methyl)formamide (2.56 g, 85% yield) as a colorless oil. LCMS: RT=1.99 min [M+H] 422.0 (Phenomenex Luna C18 4.6×30 mm column, eluting with 10-90% MeOH/H2O containing 0.1% TFA, 2 min gradient, flow rate 5 mL/min, wavelength 220 nm). To a solution of N-((4-fluoro-3-isopropoxyphenyl)(3-fluoro-5-(1,1,2,2-tetrafluoroethoxy)phenyl)methyl)formamide (225 mg, 0.53 mmol) in THF (2 mL) at 0° C. was added Et3N (0.4 mL, 2.9 mmol) followed by phosphorous oxychloride (74 μL, 0.80 mmol). The reaction mixture was allowed to warm to room temperature and stirred for 4 h. The reaction mixture was diluted with ice water (15 mL) and extracted with Et2O (3×15 mL). The combined organic layers were washed with sat. NaCl (20 mL), dried over anhydrous MgSO4, filtered and concentrated. The residue was purified by ISCO (12 g silica gel column, 0-50% EtOAc/hexane over 30 min) to yield 1-fluoro-4-((3-fluoro-5-(1,1,2,2-tetrafluoroethoxy)phenyl)(isocyano)methyl)-2-isopropoxybenzene (143 mg, 67% yield) as a pale yellow oil. LCMS: RT=2.13 min [M-NC] 377 (Phenomenex Luna C18 4.6×30 mm column, eluting with 10-90% MeOH/H2O containing 0. % TFA, 2 min gradient, flow rate 5 mL/min, wavelength 220 nm); 1H NMR (400 MHz, CDCl3) δ ppm 7.07-7.13 (1H, m), 6.91-7.03 (4H, m), 6.84-6.86 (1H, m), 5.78-6.04 (1H, m), 5.82 (1H, s), 4.54 (1H, ddd, J=11.97, 6.15, 6.04 Hz), 1.35 (6H, t, J=5.05 Hz).
