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General procedure for the synthesis of 3-bromo-5-nitrophenol from 2-amino-5-nitrophenol: 1. Intermediate preparation: a mixture of 2-amino-5-nitrophenol (48 g, 311 mmol) and N-bromosuccinimide (NBS, 57.6 g, 324 mmol) in acetonitrile (1.75 L) was stirred for 1 hr at room temperature, followed by vacuum concentration. 2. The resulting brown precipitate was dissolved in ethanol (1 L) and sulfuric acid (28 ml, 525 mmol) was added. 3. The mixture was heated to reflux and maintained for 30 min, then sodium nitrite (53.7 g, 779 mmol) was added. 4. The reaction mixture was continued to be heated for 1 hour and then concentrated. 5. The concentrated residue was partitioned between water and ethyl acetate. 6. The phases were separated and the organic phase was washed sequentially with water, saturated aqueous sodium bicarbonate and brine, followed by drying and vacuum concentration. 7. The crude product was purified by column chromatography to give 3-bromo-5-nitrophenol (32 g, 45% yield).

[1] Patent: WO2011/119704, 2011, A1. Location in patent: Page/Page column 44
[2] Patent: US2013/252938, 2013, A1
[3] Bioorganic and Medicinal Chemistry Letters, 2013, vol. 23, # 24, p. 6598 - 6603
[4] Patent: WO2006/125208, 2006, A1
[5] Patent: WO2007/148093, 2007, A1