[Synthesis]
The general procedure for the synthesis of 4-hexylpyridine from 1-bromopentane was as follows: 4-methylpyridine (2.5 g, 26.84 mmol) was dissolved in anhydrous THF (12 mL), and the solution was cooled to -78 °C using an acetone-dry ice bath. Under the condition of keeping the internal temperature below -50 °C, n-butyllithium (12.35 mL, 30.87 mmol) was slowly added. The reaction mixture was gradually warmed to 0 °C and subsequently stirred at 40 to 45 °C for 2 hours. THF (12 mL) was added to dissolve the formed 4-pyridyl lithium slurry to give a dark orange solution. The solution was cooled to 0 °C and then a solution of THF (5.0 mL) in 1-bromopentane (3.66 mL, 29.52 mmol) was carefully added at -78 °C. The internal temperature was kept below -65 °C during the addition. The reaction mixture was gradually warmed to room temperature and stirred overnight. The reaction was quenched by the addition of water (1-1.5 mL). The crude product was purified by rapid silica gel filtration (RSF), eluting with EtOAc (6 times the volume of the column) and the solvent was removed by rotary evaporator. The residue was further purified by fast chromatography (Hex/EtOAc 1.5/1) and the combined fractions were concentrated by rotary evaporator to afford 4-hexylpyridine (2.85 g, 65%) in light yellow liquid form.1H NMR (200 MHz, CDCl3): δ 8.46 (2H, d, J = 6.5 Hz, CH(2,6)), 7.09 (2H. d, J = 6.5 Hz, CH(3,5)), 2.59 (2H, t, J = 7.6 Hz, CH2(1')), 1.62 (2H, m, CH2(2')), 1.24 (6H, m, CH2(3',4',5')), 0.89 (3H, m, CH3(6')). |