Sodium hydroxide (5. 84 g, 146 mmol) was dissolved in 300 mL of water, p-methylphenylboronic acid (10. 00 g, 73 ) was added.
mmol), and add potassium permanganate (23. 05 g, 146 mmol) in water (500 mL) slowly in batches. After addition, the temperature was raised to 100 C .
Reflow and stir the reaction overnight. After the reaction was complete, the temperature was lowered to 50 , 200 mL of ethanol was added, the manganese dioxide was removed by filtration, and the filtrate was concentrated to 100 mL.
The filtrate was concentrated to 100 mL. The concentrate was slowly adjusted to acid with hydrochloric acid, a precipitate was generated, filtered, and the filter cake was washed with a small amount of water and recrystallized with water to obtain 4-carboxyphenylboronic acid (10. 30 g, 85%) as a colorless solid.
