General procedure for the synthesis of 4-methoxy-2,3-dimethylbenzoic acid from 4-methoxy-2,3-dimethylbenzaldehyde: 60.0 g of 4-methoxy-2,3-dimethylbenzaldehyde was dissolved in 1.20 L of dimethyl sulfoxide. Subsequently, a solution prepared by dissolving 131.5 g of sodium dihydrogen phosphate and 132.2 g of sodium chlorite in 480 mL of water was added dropwise, during which the reaction temperature was controlled not to exceed 40 °C. After addition, the reaction mixture was continued to be stirred at room temperature for 2 hours. Upon completion of the reaction, the suspension was diluted with 2.0 L of water, the precipitate was collected by filtration, washed with water and dried under vacuum at 100 °C to afford 65.0 g of the target product 4-methoxy-2,3-dimethylbenzoic acid as a colorless solid with a melting point of 214 °C (MS: 181.2 [MH+]).
