General procedure for the synthesis of 4-hydroxy-3-methylphenylboronic acid from 2-methyl-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenol:
1. sodium periodate (4.22 g, 19.74 mmol) and ammonium acetate (1.52 g, 19.74 mmol) were added to a mixed solution of acetone and water (2:1, 66 mL) of 2-methyl-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenol (1.54 g, 6.58 mmol) at room temperature.
2. The reaction mixture was stirred for 19 hours, followed by filtration and concentration.
3. Sodium chloride was added to the concentrated filtrate and extracted with ethyl acetate.
4. The organic layers were combined, dried with anhydrous magnesium sulfate, filtered and concentrated.
5. the residue was purified by silica gel chromatography with gradual transition of the eluent from 1:1 ethyl acetate:hexane to pure ethyl acetate to afford 364.4 mg (36% yield) of 4-hydroxy-3-methylphenylboronic acid as a solid.
Product Characterization:
1H NMR (400 MHz, d6-DMSO): δ 9.31 (s, 1H), 7.55 (s, 1H), 7.52 (d, J = 8 Hz, 1H), 6.76 (d, J = 8 Hz, 1H), 2.14 (s, 3H).
ESI-LCMS m/z 151 (M-H)-.
