Method for refining seratrodast

[0012] In a 1000mL four-neck flask, add 5.4g of crude product seltroxast with a content of 95.3%, 500mL of ethyl acetate, and 230mL of 5% aqueous sodium bicarbonate solution, stir at 0-35°C until it dissolves, and control the final pH to 8.0- 11.5, stir for 0.5 hour, separate the phases, add 4 g of activated carbon to the organic phase, stir for 0.5 hour, and filter with suction. Transfer the filtrate to a 500mL four-neck flask, add 50mL of isopropanol, control the temperature at 20±3°C, add 5N-HCl solution dropwise, control the final pH=4.0, grow crystals, filter with suction, and wash with purified water until no chloride ions are detected . After vacuum drying at 40-50°C, 32.3 g of bright yellow seltroxast crystals were obtained, with a content of 99.2%.

[0014] Add 2.8Kg of 96.4% crude setroxast, 42L of ethyl acetate, and 18L of 5% aqueous sodium bicarbonate solution into a 100L enamel jar, stir at 0-35°C until it dissolves, and control the final pH to 8.0-11.5. Stir for 0.5 hour, separate the phases, add 0.3 kg of activated carbon to the organic phase, stir for 0.5 hour, and filter with suction. Transfer the filtrate into a 100L crystallization tank, add 5L of ethanol, control the temperature at 20±3°C, add 5N-HCl solution dropwise, control the final pH=4.5, grow crystals, filter with suction, and wash with purified water until no chlorine ions are detected. After vacuum drying at 40-50°C, 2.58 kg of bright yellow seltroxast crystals were obtained, with a content of 99.4%.

[0016] Add 62.3Kg of 97.8% crude setroxast, 910L of ethyl acetate, and 270L of 5% aqueous sodium bicarbonate solution into a 1000L enamel tank, stir until it dissolves at 0-35°C, and control the final pH to 8.0-11.5. Stir for 0.5 hour, separate the phases, add 6.5Kg of activated carbon to the organic phase, stir for 0.5 hour, and filter with suction. Transfer the filtrate into a 1000L crystallization tank, add 180L acetone, control the temperature at 20±3°C, add 5N-HCl solution dropwise, control the final pH=3.8, grow crystals, filter with suction, and wash with purified water until no chlorine ions are detected. Vacuum drying at 40-50°C yielded 60.5 kg of bright yellow seltroxast crystals with a content of 98.9%.