The general procedure for the synthesis of 4-hydroxy-2-methylphenylboronic acid from 3-methyl-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenol is as follows:
1. sodium periodate (2.39 g, 11.15 mmol) was added to acetone and water (2:1, 36 mL) containing 3-methyl-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenol (870.4 mg, 3.72 mmol) and ammonium acetate (859.8 mg, 11.15 mmol) in a room temperature in a mixed solution.
2. The reaction mixture was stirred for 68 hours, then filtered and concentrated. 3.
3. Sodium chloride was added to the concentrated filtrate and extracted with ethyl acetate. 4.
4. The organic layer was dried with anhydrous magnesium sulfate, followed by filtration and concentration. 5.
5. The residue was purified by silica gel chromatography using 1:4 ethyl acetate:hexane as eluent to afford 275.7 mg (49% yield) of 4-hydroxy-2-methylphenylboronic acid as a solid.
Product characterization data:
1H NMR (400 MHz, d6-DMSO): δ 9.28 (s, 1H), 7.70 (d, J = 9 Hz, 1H), 6.56-6.52 (m, 2H), 2.55 (s, 3H).
ESI-LCMS m/z 151 (M-H)-.
