General procedure for the synthesis of 2,4-dichloro-6-aminophenol from 2,4-dichloro-6-nitrophenol: To a suspension of 2,4-dichloro-6-nitrophenol (60.0 g, 288 mmol) in ethanol (250 mL) and water (250 mL) was added sodium bisulfite (251 g, 1.44 mol) in batches. The reaction mixture was stirred at 65 °C for 4 hours. Upon completion of the reaction, the mixture was concentrated under vacuum and subsequently diluted with saturated aqueous sodium bicarbonate (500 mL) and extracted with ethyl acetate (200 mL x 4). The extracted organic layer was washed with brine and then dried with anhydrous magnesium sulfate. The dried organic layer was filtered and concentrated in vacuum. The residue was purified by silica gel EPO fast column chromatography with an eluent of 0-50% ethyl acetate/hexane gradient mixture. The target fractions were collected and the filtrate was concentrated in vacuum to give a solid product. The solid was washed with hexane to give a final 2,4-dichloro-6-aminophenol (30.6 g, 172 mmol, 60% yield) as a colorless powder. The product was confirmed by 1H NMR (CDCl3): δ 3.92 (s, 2H), 5.36 (s, 1H), 6.59 (d, J = 2.1Hz, 1H), 6.71 (d, J = 2.1Hz, 1H). Results of mass spectrometry analysis: MS Calcd.: 177; MS measured value: 178 (M + H).
