Synthesis of 1-bromo-5-methylhexane (25): to a stirred solution of LiBr (6.26 g, 72.0 mmol) in DMF (40 mL) was slowly added a solution of compound 24 (6.60 g, 24.4 mmol) in DMF (6 mL). The reaction mixture was stirred continuously at 45 °C for 3 hours. Upon completion of the reaction, the reaction was quenched by the addition of water (100 mL) and the reaction product was extracted several times with ether (5 × 250 mL). The organic phases were combined and concentrated under reduced pressure to remove the solvent to give the crude product. After purification, the target product 25 (2.40 g, 13.4 mmol, 55% yield) was obtained. The structure of the product was determined by 1H NMR (400 MHz, CDCl3) δ 0.88 (6H, d, J = 6.6 Hz), 1.19 (2H, m), 1.42 (2H, m), 1.54 (1H, m), 1.83 (2H, m), 3.41 (2H, t, J = 6.9 Hz); 13C NMR (100 MHz, CDCl3) δ 22.5, 26.0, 27.8, 33.1, 34.1, 38.0; MS (EI) m/z 179 (M+, 80), 163 (14), 155 (9), 137 (100); exact mass calculated value C6H12Br ([M-CH3]+) 163.0122, confirmed by measured value 163.0121.
