[Synthesis]
a-9) Preparation of furo[2,3-c]pyridine-5-carbaldehyde: Furo[2,3-c]pyridin-5-ylmethanol (521 mg, 3.49 mmol) was dissolved in acetone (17 mL), followed by the addition of 2,2,6,6-tetramethylpiperidin-1-yloxy (27 mg, 170 μmol). Under ice bath cooling conditions, 1,3,5-trichloro-2,4,6-triazinetrione (892 mg, 3.84 mmol) was slowly added to the reaction mixture and the reaction was stirred at the same temperature for 5 min. After completion of the reaction, the mixture was concentrated under reduced pressure, cooled to 0°C and then water and saturated aqueous sodium bicarbonate were added sequentially and extracted with ethyl acetate. The organic layer was washed with saturated brine, dried over anhydrous sodium sulfate and subsequently concentrated under reduced pressure. The resulting crude product was purified by silica gel column chromatography (eluent: hexane/ethyl acetate) to afford furo[2,3-c]pyridine-5-carbaldehyde (488 mg, 95% yield) as a yellow solid.1H-NMR (CDCl3) δ: 6.98 (1H, dd, J = 0.8, 2.2 Hz), 7.88 (1H, d, J = 2.2 Hz), 8.32 ( 1H, d, J = 0.8 Hz), 9.03 (1H, s), 10.18 (1H, s). |
[References]
[1] Patent: US2010/280013, 2010, A1. Location in patent: Page/Page column 53
[2] Journal of Medicinal Chemistry, 2006, vol. 49, # 14, p. 4425 - 4436
[3] Patent: WO2004/52894, 2004, A1. Location in patent: Page 35 |