The general procedure for the synthesis of 2,4-dimethylphenylboronic acid from triisopropyl borate and 2,4-dimethylbromobenzene was as follows: 3.42 g (0.140 mol) of magnesium and 9 mL of tetrahydrofuran were added to a reaction vessel fitted with a dropping funnel under nitrogen protection. Subsequently, a solution consisting of 20.0 g (0.108 mol) of 2,4-dimethylbromobenzene dissolved in 60 mL of tetrahydrofuran (Eq. I-4-1) was added dropwise to prepare the Grignard reagent. After the reaction mixture was stirred for 2 hours, 14.6 g (0.140 mol) of trimethyl borate was added slowly and dropwise. After continued stirring for 2 hours, hydrochloric acid was added and stirred for 1 hour. Upon completion of the reaction, the organic layer was separated, washed with brine, and then the solvent was removed by distillation to afford 15.4 g (0.103 mol) of 2,4-dimethylphenylboronic acid (Formula I-4-2).
