In a three-necked 500 mL round-bottomed flask equipped with a mechanical stirrer, dimethyl isophthalate (20.00 g, 0.103 mol, 1 equiv) was dissolved in acetone (200 mL). A methanol (40 mL) solution of NaOH (4.33 g, 0.108 mol, 1.05 eq.) was added dropwise to this solution over 20 minutes. The resulting emulsion suspension was stirred at room temperature overnight. Subsequently, another portion of NaOH (0.433 g, 0.011 mol, 0.1 eq.) was added to the reaction system and the suspension was continued to be stirred for 5 hours. The solvent was removed by distillation under reduced pressure and the resulting white precipitate was dissolved in water (400 mL). Concentrated hydrochloric acid (15 mL) was added slowly and dropwise until the pH was about 1. The suspension was filtered, and the collected precipitate was washed with water (4 x 100 mL) and dried under vacuum at 65 °C for 24 h to give a white solid of 18.25 g. The resulting monomethyl isophthalate can be used directly without further purification. Monomethyl isophthalate (5.00 g, 0.027 mol, 1 eq.) was dissolved in anhydrous tetrahydrofuran (125 mL) under nitrogen protection in a three-necked, 500 mL round-bottomed flask fitted with a magnetic stirrer and a cryogenic thermometer. The solution was cooled in an ice-water bath and a solution of BH3-SMe2 (2 M in THF, 70 mL, 0.14 mol, 5 eq.) was added slowly and dropwise over 90 min, keeping the reaction temperature below 7 °C. After the dropwise addition was completed, the reaction was continued for 15 min, after which the cooling bath was removed to bring the reaction system to room temperature. After 5 hours of reaction, the reaction was carefully quenched with small pieces of ice (note the violent gas release) while keeping the ice-water bath cool. When gas release ceased, brine (50 mL) was added and the mixture was extracted with ether (3 x 100 mL). The organic extracts were combined and washed sequentially with diluted bleach (50 mL, diluted 10-fold from initial 9.6% bleach), brine (50 mL), and dried with anhydrous magnesium sulfate. The solvent was removed by distillation under reduced pressure to give an oil containing a small amount of white precipitate. Add ether (20 mL), filter to remove the solid, and wash the solid with ether (2 × 10 mL). The filtrate was concentrated to give a light yellow oil (4.48 g). Purification of the crude product by silica gel column chromatography (petroleum ether: ethyl acetate, 4:1 to 7:3) afforded methyl 3-hydroxymethylbenzoate (2d) as a colorless oil (3.77 g, 82% yield). rf = 0.17 (ethyl acetate: petroleum ether = 1:4); 1H NMR (300 MHz, CDCl3), δ (ppm): 8.00 (s, 1H, HAr ), 7.93 (dt, J = 7.7,1.4 Hz, 1H, HAr), 7.61-7.51 (m, 1H, HAr), 7.40 (t, J = 7.7 Hz, 1H, HAr), 4.71 (s, 2H, OCH2), 3.89 (s, 3H, OMe).
