General procedure for synthesizing 2-hydroxy-4,5-dimethoxybenzoic acid from methyl 2-hydroxy-4,5-dimethoxybenzoate: sodium hydroxide (0.75 mol) and 100 mL of water were added to a reaction flask and stirred until clarified. Methyl 2-hydroxy-4,5-dimethoxybenzoate (0.25 mol) was suspended in the above alkaline solution according to the preparation method of Example 1 and stirred at room temperature for about 3.0 hours. The reaction progress was monitored by TLC, and after confirming the completion of the reaction, the reaction system was cooled to 10 °C, and the pH was adjusted slowly and dropwise to 4.0 by adding dilute hydrochloric acid.Subsequently, stirring, filtration, and drying were carried out, and 47.4 g of 2-hydroxy-4,5-dimethoxybenzoic acid was obtained, with a molar yield of 95.2% and a purity of 99.5% by HPLC.
