Sodium borohydride (0.38 g, 11 mmol) was added to a solution of (4-formylphenyl)boronic acid (1.5 g, 11 mmol) in methanol (40 mL) in batches at 0 °C, keeping the temperature at 0 °C and stirring the reaction mixture for 1 hour. Upon completion of the reaction, the mixture was concentrated under reduced pressure to remove the solvent to give the crude product. The crude product was dissolved in water, cooled to 0-5 °C, and the pH was adjusted to 5 by slowly adding 5% aqueous acetic acid.The precipitated solid was collected by diafiltration and washed with cold water, and dried to give 4-hydroxymethylphenylboronic acid (1.2 g, 80% yield). The product was characterized by 1H NMR (400 MHz, CD3OD): δ 7.72 (d, J=7.2 Hz, 2H), 7.59 (d, J=7.6 Hz, 2H), 7.35-7.30 (m, 2H), 4.60 (s, 2H); Mass Spectrometry (ES+): m/z 542.15,544.35 [M+H]; LCMS retention time: tR = 2.42 min.
