Synthesis
General procedure for the synthesis of 2-amino-6-bromobenzoic acid from 4-bromoindoline-2,3-dione: Commercially available 4-bromoindigo (2.50 g, 11.1 mmol) was dissolved in 1.5 mol/L aqueous sodium hydroxide solution (20 mL), and 33% aqueous hydrogen peroxide solution (1 mL) was added slowly and dropwise at 55 °C. The reaction mixture was stirred continuously at 55 °C for 30 min and then cooled to room temperature. Subsequently, the reaction solution was neutralized with 2.0 mol/L hydrochloric acid solution and finally purified by HP-20 resin column to obtain the target product 2-amino-6-bromobenzoic acid (1.60 g, 67% yield).
References
[1] Patent: EP2708540, 2014, A1. Location in patent: Paragraph 0092
[2] Proceedings of the Royal Society of London, Series B: Biological Sciences, 1958, vol. 148, p. 481,488
[3] Patent: WO2011/28741, 2011, A1. Location in patent: Page/Page column 202
[4] ACS Medicinal Chemistry Letters, 2016, vol. 7, # 9, p. 831 - 834
