Sodium Nitrate → 2-Bromo-4-fluoro-6-nitrophenol

2-Bromo-4-fluoro-phenol 2a (8.0 g, 41.9 mmol) was dissolved in 10 mL of sulfuric acid (50%) followed by addition of a solution of sodium nitrate (7.1 g, 83.5 mmol) in 24 mL of sulfuric acid (25%), upon cooling by an ice-water bath. The reaction mixture was reacted at room temperature for 1.5 hours and the reaction was monitored by TLC until the disappearance of the starting materials. The mixture was diluted with 50 mL of water and extracted with ethyl acetate (50 mL×2). The combined organic extracts were washed with water and saturated aqueous sodium bicarbonate and dried over anhydrous magnesium sulfate, filtered and concentrated under reduced pressure to obtain the title compound 2-bromo-4-fluoro-6-nitro-phenol 2b (8.0 g, yield 80.8%) as a red solid, which was directly used in the next step.