The general procedure for the synthesis of bis(3-amino-4-hydroxyphenyl)sulfone from 3,3'-dinitro-4,4'-dihydroxydiphenylsulfone was as follows: 3.4 kg of 3,3'-dinitro-4,4'-dihydroxydiphenylsulfone, 9.5 kg of dimethylsulfoxide (DMSO), and 3.18 kg of aqueous 5.3% ammonium chloride were added to a reactor, and the temperature was slowly raised to 50°C. Subsequently, 2.5 kg of reduced iron powder was added in batches (material molar ratio of 3,3'-dinitro-4,4'-dihydroxydiphenylsulfone: iron: chlorinated iron). 2.5 kg of reduced iron powder was added in batches (material molar ratio of 3,3'-dinitro-4,4'-dihydroxydiphenylsulfone: iron: ammonium chloride: water: DMSO = 1:4.5:6:29:12). After completion of the reaction, hot filtration was performed and the filter cake was washed with hot DMSO. The filtrates were combined and evaporated under reduced pressure to give a mixed solution of DMSO and water, which was cooled to 5°C to promote precipitation of the product. After stopping the distillation, the solid product was collected by filtration, washed with water and dried to give 2.6 kg of 3,3'-diamino-4,4'-dihydroxydiphenyl sulfone in 93% yield.
