The general procedure for the synthesis of 5-methoxy-2-methylphenylboronic acid from 3-bromo-4-methylanisole was as follows: 2.5 M n-butyllithium (nBuLi, 1.8 mL, 4.5 mmol) was added slowly and dropwise over a period of 5 min to 2-bromo-4-methoxy-1-methylbenzene (750 mg, 3.73 mmol) in an anhydrous tetrahydrofuran (THF,) at -78 °C. 30 mL) solution. The reaction mixture was stirred at -78 °C for 20 min before adding anhydrous trimethylborate (0.62 g, 6 mmol). The reaction mixture was warmed to room temperature and kept for 2 hours. The reaction was quenched by addition of 2N hydrochloric acid (HCl, 1 mL). THF was removed by distillation under reduced pressure. the crude product was diluted with 2N HCl (100 mL) and extracted with ethyl acetate (2 x 50 mL). The combined organic phases were dried with anhydrous sodium sulfate, filtered and concentrated under reduced pressure to give a light yellow solid product (0.43 g, 69% yield).
