Synthesis
Step B-1: Synthesis of 1-(6-fluoropyridin-2-yl)ethanone
1. dissolve 6-fluoro-N-methyl-N-(methoxy)-2-pyridinecarboxamide (1.10 g, 5.97 mmol) in 40 mL of anhydrous THF under stirring conditions and cool the solution to 0°C. 2. add methylmagnesium chloride (8.0 mL, 3.0 M in THF) via a syringe.
2. Methylmagnesium chloride (8.0 mL, 3.0 M solution in THF, 24 mmol) was added slowly via syringe, keeping the reaction temperature at 0°C.
3. The reaction mixture was stirred at 0°C for 30 min.
4. The reaction was burst by the addition of saturated ammonium chloride solution (20 mL).
5. Pour the reaction mixture into a separatory funnel, add water (20 mL) and ether (30 mL), shake well and leave to stratify.
6. Separate the organic layer and extract the aqueous layer with ether (2 × 20 mL).
7. Combine all organic layers and wash with saturated brine (20 mL).
8. The organic layer was dried with anhydrous magnesium sulfate, filtered, and the filtrate was concentrated under reduced pressure to obtain the crude product.
9. The crude product was purified by column chromatography to afford 1-(6-fluoropyridin-2-yl)ethanone (0.746 g, 90% yield).
10. The structure of the product was confirmed by 1H NMR (300 MHz, DMSO-d6): δ 8.24 (m, 1H), 7.94 (ddd, J = 7.4, 2.5, 0.7 Hz, 1H), 7.54 (dd, J = 8.2, 2.7, 0.7 Hz, 1H), 2.62 (s, 3H).
References
[1] Patent: US2008/300247, 2008, A1. Location in patent: Page/Page column 120
[2] Patent: WO2007/143456, 2007, A2. Location in patent: Page/Page column 261
