(Step 1) Synthesis of 3,5-difluoro-2-nitrophenol: Dimethyl sulfoxide (DMSO, 50 mL) and 10 N sodium hydroxide solution (12 mL, 120 mmol) were added to a reaction flask, followed by 1,3,5-trifluoro-2-nitrobenzene (10.0 g, 56.5 mmol). The reaction mixture was stirred at room temperature for 15 hours. Upon completion of the reaction, water (100 mL) and ether (200 mL) were added for stratification. The aqueous layer was collected, acidified with 1 N hydrochloric acid and extracted with ether (2 x 200 mL). The organic phases were combined, dried with anhydrous magnesium sulfate, and the solvent was removed by distillation under reduced pressure. The crude product was purified by silica gel column chromatography using chloroform-ethyl acetate (10:1, v/v) as eluent to afford the title compound 3,5-difluoro-2-nitrophenol (7.97 g, 81% yield) as a yellow crystalline powder.1H-NMR (CDCl3) δ: 6.53-6.59 (m, 1H), 6.66-6.70 (m, 1H), and 10.87 (d, J = 1.2 Hz, 1H).
