[Synthesis]
Step 1. Synthesis of 5-fluoro-N-methylpyridin-2-amine: A suspension of sodium hydride (60% dispersed in mineral oil, 117.8 mg, 4.91 mmol) was made in dry tetrahydrofuran (25 mL). Subsequently, a solution of 5-fluoropyridin-2-amine (500 mg, 4.46 mmol) in tetrahydrofuran (25 mL) was added dropwise to this suspension. The reaction mixture was stirred at room temperature and maintained at 40 °C for 30 min. After that, the reaction system was cooled to -40 °C and methyl iodide (696.9 mg, 4.91 mmol) was slowly added. After addition, the reaction mixture was returned to room temperature and stirred overnight. Upon completion of the reaction, the reaction was quenched by the addition of water and the mixture was extracted with ethyl acetate. The organic phases were combined, dried over anhydrous sodium sulfate and concentrated under reduced pressure. The resulting crude product was purified by fast column chromatography on silica gel with hexane/ethyl acetate (4:1, v/v) as eluent to give 129 mg of the title compound in 23% yield. The product was characterized by 1H-NMR (CDCl3): δ 7.97 (1H, d, J = 2.6 Hz), 7.28-7.17 (1H, m), 6.34 (1H, dd, J = 3.5, 9.1 Hz), 2.90 (3H, d, J = 5.1 Hz). |