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Under nitrogen atmosphere, 3,5-dibromopyridine-4-carboxaldehyde (80 g, 303 mmol) and cesium carbonate (98 g, 302 mmol) were sequentially added to a 2L round-bottomed flask containing tetrahydrofuran (1.3 L). Methyl mercaptoacetate (32 g, 302 mmol) was then added and the reaction mixture was stirred at 60 °C overnight. After completion of the reaction, it was cooled to room temperature and extracted by adding ethyl acetate. The organic layer was washed sequentially with water, saturated aqueous sodium bicarbonate solution and brine, dried over anhydrous sodium sulfate and filtered to give a white solid crude product. The crude product was purified by recrystallization from ethyl acetate to finally obtain methyl 4-bromothieno[2,3-C]pyridine-2-carboxylate (60 g, 73% yield).

[1] Patent: WO2013/127266, 2013, A1. Location in patent: Page/Page column 135
[2] Patent: WO2013/127267, 2013, A1. Location in patent: Page/Page column 86; 87
[3] Patent: WO2013/127268, 2013, A1. Location in patent: Page/Page column 64; 65
[4] Patent: WO2013/130935, 2013, A1. Location in patent: Paragraph 0188
[5] Journal of Heterocyclic Chemistry, 2008, vol. 45, # 1, p. 91 - 96