2,4,5-Trimethoxybenzoic acid

PreparationThe preparation steps of the pharmaceutical intermediate 2,4,5-trimethoxybenzoic acid are as follows: Step 1: Add 4.42g of 1,2,4-trimethoxybenzene and 10ml of DMF to a reaction flask. Heat in an ice-water bath at 10℃. Add a DMF solution containing 1.47g of phosphorus oxychloride dropwise. After the addition is complete, heat the mixture to 60℃ and stir for 1 hour. Step 2: Control the reaction via TLC. If the reaction is complete, pour the reaction solution into 30ml of cold water. Add 30% potassium hydroxide solution to adjust the pH to 7. Cool to 5℃ and allow crystallization for 30 minutes. Filter and wash to obtain 2,4,5-trimethoxybenzaldehyde. Step 3: Add 5g of 2,4,5-trimethoxybenzaldehyde and 1.5g of ZnO to a reaction flask. rO2/MCM-41 nanocatalyst, 10 mol% silver nitrate, and 50 ml acetonitrile were added dropwise with 8.7 g of 30% hydrogen peroxide solution at room temperature. After the addition was complete, the reaction system was heated to 50°C and reacted for 3 h. Step 4: After the reaction was complete, the reaction solution was added to 50 ml of 10% cold alkaline solution and stirred. The insoluble substances were filtered out, and the pH of the filtrate was adjusted to 3.5 with concentrated sulfuric acid. Extraction was performed with ethyl acetate (2 × 50 ml), and the organic phases were combined. The mixture was washed once with saturated sodium chloride, dried over magnesium sulfate, concentrated, and recrystallized from benzene and petroleum ether to give a white crystalline product, 2,4,5-trimethoxybenzoic acid.