A. Synthesis of 4-n-butylphenylboronic acid
To a mixed solution of tetrahydrofuran (32 mL) and ether (96 mL) of 1-bromo-4-n-butylbenzene (6.24 g, 29.3 mmol) was added dropwise n-butyllithium (1.6 M hexane solution, 21.9 mL, 35.1 mmol) at -78 °C. The reaction mixture was stirred at -78 °C for 30 min, and then slowly added dropwise over 20 min to a solution of trimethyl borate (6.1 g, 58.6 mmol) in ether (64 mL) pre-cooled to -78 °C. After the dropwise addition was completed, the reaction mixture was continued to be stirred at -78 °C for 30 minutes, then slowly warmed to room temperature and stirred overnight. After the reaction was completed, 10% aqueous hydrochloric acid solution (150 mL) was added, shaken vigorously for 10 minutes, and left to stratify. The ether layer was separated and the aqueous layer was extracted with ether (100 mL). All organic phases were combined and extracted with 1N sodium hydroxide solution (3 x 100mL). Combine the alkaline aqueous phases, wash once with ether, then acidify to pH 1 with 6N hydrochloric acid and extract with ether (3 x 100mL). All organic phases were combined, washed with water, dried with anhydrous magnesium sulfate, and concentrated under reduced pressure to afford the target product 4-n-butylphenylboronic acid (2.0 g, 38% yield).
