In 3,4-dimethoxy-6-nitrobenzaldehyde (10 g)The reaction medium (20 mL of water, 30 mL of methanol)Acetic acid (3.5 mL), 30% hydrogen peroxide (9 mL)Stir well and add sodium chlorite (content 80%, 9g) in water (5mL); Stirring warming to about 50, monitoring the reaction, After the reaction was completed, sodium bisulfite (10.5 g) was added to quench the reaction, The solvent was evaporated to dryness, the product was dissolved in a solution of sodium hydroxide (6g × 10mL)Filtered to remove impurities, the filtrate was added sulfuric acid to pH 1 precipitated product, Filter and dry and obtained product 4,5-Dimethoxy-2-nitrobenzoic acid 10g (93% yield, high-performance liquid chromatography 99.5% purity).