General procedure for the synthesis of 5-(benzyloxy)-2-hydroxybenzoic acid from 2,5-dihydroxybenzoic acid and benzyl bromide: 60% NaH (100 mg, 2.2 mmol) was suspended in DMF (5 mL) at room temperature, followed by the addition of 2,5-dihydroxybenzoic acid, and the reaction mixture was stirred for 1 hour. Next, benzyl bromide (0.119 mL, 1 mmol) was slowly added dropwise to the above solution and the reaction continued to be stirred for 7 hours. Upon completion of the reaction, the reaction was quenched by the addition of H2O (20 mL) and the reaction mixture was acidified to pH 1-3 with 1 N HCl. The reaction mixture was extracted with EtOAc (20 mL), the organic phase was washed with brine (3 x 20 mL) and dried over anhydrous Na2SO4. The solvent was removed by concentration under reduced pressure and the residue was purified by fast chromatography (eluent: petroleum ether/ethyl acetate = 1:1) to afford the target compound 5-(benzyloxy)-2-hydroxybenzoic acid (3a) as a white solid (54 mg, 22% yield).
[1] European Journal of Organic Chemistry, 2004, # 23, p. 4864 - 4869
[2] Journal of the American Chemical Society, 2011, vol. 133, # 32, p. 12433 - 12435
[3] Bioorganic and Medicinal Chemistry, 2011, vol. 19, # 16, p. 4935 - 4952