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General procedure for the synthesis of 7-bromofuro[3,2-c]pyridin-4(5H)-ones from 4,5-dihydro-4-oxofuro[3,2-c]pyridine: To a stirred mixture of 4,5-dihydro-4-oxofuro[3,2-c]pyridine (5 g, 37.0 mmol) in acetonitrile (50 mL) at 0 °C, N-bromosuccinimide ( NBS, 8.56 g, 48.1 mmol) solution in acetonitrile, with an addition time of 0 min. The reaction mixture was continued to be stirred at 0 °C for 1 h, followed by slow warming to room temperature and stirring for 10 min. Upon completion of the reaction, water (250 mL) and saturated aqueous sodium bicarbonate solution (10 mL) were added to the mixture. The precipitated off-white solid was collected by filtration and dried to afford 7-bromofuro[3,2-c]pyridin-4(5H)-one (1.5 g, 5.96 mmol, 16.10% yield). The product was characterized by 1H NMR (400 MHz, CD3OD): δ 7.82 (d, J=2.0 Hz, 1H), 7.51 (s, 1H), 7.05 (d, J=2.4 Hz, 1H); ES-LCMS m/z: 214.0, 215.9 ([M+H]+).

[1] Bioorganic and Medicinal Chemistry Letters, 2005, vol. 15, # 4, p. 899 - 903
[2] Patent: WO2016/37578, 2016, A1. Location in patent: Page/Page column 146; 147
[3] Patent: WO2003/76442, 2003, A1. Location in patent: Page/Page column 38-39