Under argon protection, 2,3-dimethoxyterephthalaldehyde (2,3-DMTA, 0.5 g, 2.51 mmol) was dissolved in dichloromethane (CH2Cl2, 22 mL). To this solution was slowly added boron tribromide (BBr3, 1 M in CH2Cl2, 10.3 mL). The reaction mixture was stirred at room temperature for 4 hours. Subsequently, the reaction was quenched by the addition of water (22 mL) and stirring was continued overnight. After completion of the reaction, the mixture was extracted with chloroform (CHCl3), the organic layers were combined and dried with anhydrous magnesium sulfate (MgSO4). After filtration to remove the desiccant, the filtrate was concentrated to dryness under reduced pressure. The resulting residue was recrystallized by dichloromethane/hexane mixed solvent to give 2,3-dihydroxyterephthalaldehyde in 89% yield. The product was characterized by 1H NMR (CDCl3, 400 MHz): δ (ppm) 10.90 (s, 2H), 10.03 (s, 2H), 7.28 (s, 2H).
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