General procedure for the synthesis of 4-bromo-5-fluoro-2-nitroaniline from 4-bromo-5-fluoro-2-nitroaniline: to a solution of 4-bromo-5-fluoro-2-nitroaniline (1.0 g, 4.3 mmol) in THF (9.0 mL) was added EtOH (9.0 mL) and H2O (3 mL), followed by the addition of iron powder (1.2 g, 21.3 mmol) and ammonium chloride (0.34 g, 6.4 mmol). The reaction mixture was heated to reflux at 95 °C for 4 hours. After completion of the reaction, the mixture was cooled to room temperature, diluted with EtOH and filtered through a diatomaceous earth pad until the filtrate was colorless. The filtrate was concentrated under reduced pressure, the residue was dissolved in EtOAc, washed sequentially with H2O and brine, the organic phase was dried with anhydrous Na2SO4, filtered and concentrated. Hexane was added to the concentrate and the precipitated solid was collected by filtration to afford the title compound 4-bromo-5-fluorobenzene-1,2-diamine (710 mg, 3.5 mmol, 81% yield).
