3-Bromo-5-methylphenylboronic acid

Synthesis

5419-55-6

1611-92-3

849062-36-8

The general procedure for the synthesis of (3-bromo-5-methylphenyl)boronic acid from triisopropyl borate and 3,5-dibromotoluene was as follows: 3,5-dibromotoluene (20.0 g, 80.0 mmol) was dissolved in anhydrous tetrahydrofuran (100 mL) in a dry three-neck flask. The reaction mixture was cooled to -78 °C under nitrogen protection and tert-butyllithium (5.1 g, 80.0 mmol) was slowly added to maintain the reaction temperature at -78 °C. Subsequently, triisopropyl borate (22.6 g, 120.0 mmol) was added dropwise over 30 min and the reaction continued to be stirred for 2 h at -78 °C. Upon completion of the reaction, the reaction was quenched with deionized water and the pH was adjusted to 6 with a dilute hydrochloric acid solution of 2 mol/L. The reaction mixture was extracted with ethyl acetate (50 mL x 3), the organic phases were combined and dried over anhydrous sodium sulfate. After filtration, the filtrate was concentrated under reduced pressure to remove the solvent. The resulting residue was slurried with hexane (30 mL) and dried to give 15.6 g of (3-bromo-5-methylphenyl)boronic acid as a white solid in 90.7% yield.

References