4-Hydroxybenzoic acid (2.00 g, 14.5 mmol) was suspended in dichloromethane (50 mL) and diisopropylethylamine (10.1 mL, 57.9 mmol) and chloromethylmethyl ether (2.20 mL, 29.0 mmol) were added sequentially under ice bath cooling. The reaction mixture was gradually warmed to room temperature with continuous stirring for 2.5 hours. Under ice bath cooling again, chloromethyl methyl ether (1.10 mL, 14.5 mmol) was added to the reaction mixture, followed by stirring at room temperature for 17 hours. After completion of the reaction, the solvent was removed by concentration under reduced pressure and methanol (50 mL) and 4 mol/L aqueous potassium hydroxide (50 mL) were added to the residue and stirred at room temperature for 3 hours. The solvent was again concentrated under reduced pressure to remove the solvent, and the residue was acidified with 4 mol/L hydrochloric acid, diluted with water and extracted with ethyl acetate. The organic phase was washed with saturated brine and dried over anhydrous sodium sulfate. The solvent was removed by concentration under reduced pressure to give white solid 4-(methoxymethyl)benzoic acid (2.63 g, 100% yield). The product was detected by ESI-MS showing m/z: 181 [M-H] ; 1H-NMR (CDCl3) δ (ppm): 3.37 (s, 3H), 5.26 (s, 2H), 7.00-7.16 (m, 2H), 7.80-7.96 (m, 2H), 12.65 (br s, 1H).
