Synthesis
The general procedure for the synthesis of 5-amino-2-bromo-4-methylbenzoic acid from 3-amino-4-methylbenzoic acid was as follows: 3-amino-4-methylbenzoic acid (24.72 g, 162 mmol) was dissolved in anhydrous DMF (140 mL). Subsequently, the solution was cooled to 0-5 °C and N-bromosuccinimide (29.70 g, 163.5 mmol) was added in batches while keeping the temperature of the reaction mixture below 15 °C. The reaction mixture was stirred under these conditions for 2 hours. Upon completion of the reaction, the mixture was slowly poured into an ice-water mixture (150 g) while stirring was continued. The precipitated solid was collected by filtration and washed with cold water (3 x 120 mL). The resulting filter cake was dissolved in EtOAc (800 mL) and the organic layer was washed with water (3 x 200 mL). The organic layer was subsequently dried with anhydrous magnesium sulfate, filtered and the solvent was removed by vacuum evaporation to afford 5-amino-2-bromo-4-methylbenzoic acid as a pink solid (31.59 g, 85% yield).
References
[1] European Journal of Medicinal Chemistry, 2011, vol. 46, # 7, p. 2662 - 2675
[2] Patent: WO2011/159067, 2011, A2. Location in patent: Page/Page column 28
[3] Patent: US2007/275907, 2007, A1. Location in patent: Page/Page column 19
[4] Patent: US2008/242596, 2008, A1. Location in patent: Page/Page column 15
[5] Bioorganic and Medicinal Chemistry Letters, 2009, vol. 19, # 19, p. 5632 - 5635
