A mixture of tert-butyl(4-chloro-2-fluoro-5-hydroxyphenyl)carbamate (6.70 g, 25.6 mmol), 2-chloro-5-nitropyridine (4.06 g, 25.6 mmol), potassium carbonate (3.89 g, 28.1 mmol) and N,N-dimethylformamide (70 mL) was stirred at room temperature for 30 min. To the reaction mixture was added aqueous ammonium chloride solution (100 mL), and the mixture was extracted with ethyl acetate (150 mL×3). The organic layers were combined, washed successively with water (100 mL) and saturated brine (50 mL), dried over anhydrous magnesium sulfate, and concentrated under reduced pressure to give the title compound (4.52 g, 46%) as a white powder.
