General procedure for the synthesis of 5-bromo-3-fluorobenzene-1,2-diamine from 2-fluoro-4-bromo-6-nitroaniline: to a solution of 4-bromo-2-fluoro-6-nitroaniline (0.5 g, 2.1 mmol) in tetrahydrofuran (THF, 4.6 mL) was added ethanol (EtOH, 4.6 mL) and water (H2O, 1.5 mL), followed by addition of iron powder (0.6 g , 10.6 mmol) and ammonium chloride (0.17 g, 3.2 mmol). The reaction mixture was stirred at 95 °C for 22 hours. After completion of the reaction, the mixture was cooled to room temperature and filtered through diatomaceous earth. The solid residue was washed with ethanol until the filtrate was colorless. The filtrates were combined, concentrated under reduced pressure, and the residue was dissolved in ethyl acetate (EtOAc), washed sequentially with water and saturated brine, dried over anhydrous sodium sulfate (Na2SO4), filtered, and concentrated under reduced pressure to give the title compound, 5-bromo-3-fluorobenzene-1,2-diamine (0.43 g, 99% yield), as a brown waxy solid.
