20776-48-1

20780-72-7

20776-48-1

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).