Acetic Acid → N-benzyl-N-nitroso-2-[2-(4-chloro-phenyl)-5,6-difluoro-benzoimidazol-1-yl]-2-(4,4-difluoro-cyclohexyl)-acetamide

To a ice-cold solution of 3.10 g (5.85 mMol) N-benzyl-2-[2-(4-chloro-phenyl)-5,6-difluoro-benzoimidazol-1-yl]-2-(4,4-difluoro-cyclohexyl)-acetamide in 19.1 ml (333 mmol) acetic acid and 40.14 ml (708 mmol) acetic anhydride were added in portions over 20 min. 2.02 g (29.25 mmol) sodium nitrite. The reaction mixture was stirred overnight at room temperature and evaporated. The residue was taken up in saturated aqueous sodium bicarbonate solution and ethyl acetate and the pH was adjusted to 7 by adding solid sodium bicarbonate. The aqueous layer was extracted twice with ethyl acetate and the combined organic layers were washed with brine, dried over magnesium sulfate, filtered and evaporated to dryness. Yellow foam (85%). MS (Turbo Spray): m/z=559.2 [M+H].