Synthesis
Step 1: To a stirred solution of 4-bromo-2-fluorobenzoic acid (15.0 g, 68.49 mmol, 1 eq.) in methanol (150 mL) was slowly added thionyl chloride (23.09 mL, 136.9 mmol, 2 eq.) at 0 °C. The reaction mixture was kept at 0 °C for 15 minutes before being brought to room temperature and stirring was continued for 12 hours. After completion of the reaction, methanol was removed by evaporation under reduced pressure and the residue was diluted with ethyl acetate (250 mL). The organic layer was washed sequentially with saturated aqueous sodium bicarbonate solution, brine (150 mL) and deionized water (150 mL). The ethyl acetate layer was dried over anhydrous sodium sulfate and concentrated under reduced pressure to give methyl 4-bromo-2-fluorobenzoate (15 g, 93% yield) as an off-white solid (LC-MS purity 99%; TLC conditions: ethyl acetate/petroleum ether (3:7), Rf value 0.8).
References
[1] Patent: WO2004/46096, 2004, A2. Location in patent: Page 38
[2] Organic Process Research and Development, 2011, vol. 15, # 3, p. 565 - 569
[3] Journal of Medicinal Chemistry, 2013, vol. 56, # 19, p. 7651 - 7668
[4] Patent: WO2015/48306, 2015, A1. Location in patent: Page/Page column 88; 112
[5] Patent: WO2013/68461, 2013, A1. Location in patent: Page/Page column 105; 106; 109
