General procedure for the synthesis of methyl 2,3-diamino-5-bromo-5-bromobenzoate from methyl 2-amino-5-bromo-3-nitrobenzoate: Methyl 2-amino-5-bromo-3-nitrobenzoate (0.67 g, 2.44 mmol), iron powder (0.68 g, 12.0 mmol), and ammonium chloride (1.96 g, 37.0 mmol) were dissolved in a mixture of THF/ethanol/water (1:1:0.4 v/v, total 29 mL) in a solvent mixture. The reaction mixture was heated at 95 °C and stirred vigorously for 1 hour. Upon completion of the reaction, the mixture was cooled to room temperature and filtered through a diatomaceous earth plug to remove insoluble solids. The diatomaceous earth plug was washed several times with methanol and tetrahydrofuran. The filtrate and washings were combined and concentrated under reduced pressure. The concentrated residue was partitioned between ethyl acetate and water. The organic layer was separated, washed once with saturated saline and concentrated again under reduced pressure to give methyl 2,3-diamino-5-bromobenzoate (0.59 g, 99% yield) as a yellow powder, which can be used in subsequent reactions without further purification.
