General procedure for the synthesis of 4-(2-methoxyethoxy)phenylboronic acid (E34) from 2-(4-(2-methoxyethoxy)phenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (E33):
Step 3: E33 (3.47 g, 12.50 mmol) was dissolved in acetone (75 mL) and a solution of ammonium acetate (4 equiv, 3.85 g, 49.9 mmol) in water (75 mL) was added with stirring. Sodium periodate (4 eq, 10.7 g, 49.9 mmol) was then added in batches. The reaction mixture was prepared as a yellow/white suspension and stirred vigorously for 36 hours at room temperature. After completion of the reaction, the mixture was filtered and the insoluble material was washed with ethyl acetate. The filtrates were combined, concentrated under reduced pressure and the residue was extracted several times with ethyl acetate. The organic phases were combined, dried with anhydrous magnesium sulfate and the solvent was evaporated under reduced pressure to give the crude product as a white solid. The crude product was purified by fast column chromatography (CombiFlash Rf, eluent: isohexane/ethyl acetate, gradient 0% to 70%) to give E34 as a white solid (875 mg).
1H NMR (CDCl3) δ: 8.14 (2H, d), 7.03 (2H, d), 4.20 (2H, t), 3.79 (2H, t), 3.48 (3H, s).
