Trimethyl 1,3,5-benzenetricarboxylic acid ester (62 g, 246 mmol) was used as raw material and dissolved in a mixed solution of methanol (800 mL) and water. Aqueous sodium hydroxide solution (221 mL, 221 mmol, 1 N) was added slowly under vigorous stirring. The suspension was gradually dissolved over a period of 8 hours. The reaction mixture was continued to be stirred at room temperature for 18 hours. Subsequently, the solvent was removed by vacuum distillation. Dichloromethane (600 mL) was added to the remaining solid and the organic phase was washed with saturated aqueous sodium bicarbonate. The organic layer was separated through a partition funnel and washed three times with sodium bicarbonate solution (3 x 500 mL). After filtration, the solids were rinsed with a funnel. The crude product was analyzed by LC-MS and the molecular weight was confirmed as the target product 3,5-bis(methoxycarbonyl)benzoic acid (MW: 238; 48.8 g; 83% yield). The material in the organic layer was analyzed by LC-MS as a mixture of the target product and the over-hydrolysis product 5-(methoxycarbonyl)isophthalic acid (MW: 224; 9 g), and the material in the aqueous layer was analyzed as the starting material.
