[Synthesis]
Synthesis of 5-bromo-2-tert-butylpyridine: To a suspension of copper cyanide (1.79 g, 20 mmol) in THF (40 mL), which had been dried under reduced pressure for 4 h, a tert-butylmagnesium chloride solution (40 mL, 40 mmol) in 1.0 M THF was added dropwise slowly over a period of 30 min at -78 °C. The reaction mixture was then stirred for 1 h. After the reaction was completed, the reaction was continued with stirring for 1 h. The reaction mixture was then stirred for 1 h at -78 °C. After the dropwise addition, the reaction mixture was continued to be stirred at -78 °C for 1 hour. Subsequently, 5-bromo-2-iodopyridine (2.83 g, 10 mmol) was added at the same temperature and stirred at -78 °C for 1 h. After that, the reaction mixture was warmed up to room temperature and stirred for 16 h. The reaction was completed with the addition of 25% M THF. Upon completion of the reaction, the reaction was quenched with 25% ammonia solution (40 mL), the resulting precipitate was removed by filtration and the precipitate was washed with EtOAc. The filtrate and washings were combined and concentrated under vacuum. The concentrated product was purified by silica gel column chromatography using hexane/EtOAc (20:1) as eluent to afford the target compound 5-bromo-2-tert-butylpyridine (1.07 g, 50% yield) as a colorless oil.1H NMR (300 MHz, CDCl3) δ 1.35 (9H, s), 7.24 (1H, d, J = 8.1 Hz), 7.72 (1H, d, J = 8.1 Hz) 7.72 (1H, dd, J = 2.2, 8.1 Hz), 8.61-8.62 (1H, m). |