Synthesis
2-Amino-4-methoxybenzoic acid (4.00 g, 23.93 mmol) was dissolved in DMF (120 mL) at 0 °C, followed by the addition of N-bromosuccinimide (NBS, 4.68 g, 26.3 mmol). The cooling bath was removed and the reaction mixture was allowed to gradually warm up to room temperature and stirred continuously at this temperature for 1 hour. Upon completion of the reaction, the mixture was re-cooled to 0 °C, saturated sodium sulfite solution (25 mL) was added and stirred for 5 min. The pH of the mixture was adjusted with concentrated hydrochloric acid (~10-15 mL) to 3. The reaction mixture was transferred to a split funnel containing water (100 mL) and extracted with ether (250 mL for the first time and 100 mL for the next 4 times). The organic layers were combined, washed sequentially with water (3 x 50 mL) and brine (50 mL), dried over anhydrous magnesium sulfate, filtered and concentrated to give 2-amino-5-bromo-4-methoxybenzoic acid (5.90 g, 100% yield) as a solid product. The product was confirmed by 1H NMR (400 MHz, DMSO-d6) and mass spectrometry (ESI): 1H NMR δ 7.78 (s, 1H), 6.43 (s, 1H), 3.81 (s, 3H), 2.90 (s, 1H), 2.74 (s, 1H); MS (ESI) m/e 228.0 [(M+H-H2O), calculated value C8H7BrNO2 228.0].
References
[1] Patent: WO2016/53794, 2016, A1. Location in patent: Page/Page column 111
[2] Patent: US2009/69320, 2009, A1. Location in patent: Page/Page column 68
[3] Patent: WO2014/169167, 2014, A1. Location in patent: Page/Page column 87
[4] Patent: WO2015/17589, 2015, A1. Location in patent: Page/Page column 98
