Patent ID: 7531694

Claim:
A process for synthesis of 4-4′-diamino-diphenyl-sulfone characterised by the following steps: condensation reaction of 4-aminothio-phenol and 4-chloro-nitrobenzene with formation of 4-nitro-4′-amino-diphenyl-sulfide at temperatures from 45° C. to reflux temperatures of the reaction mixture; oxidation of the thioether with an oxidising system comprising Na 2 WO 4 and H 2 O 2 into the corresponding sulfone, wherein the Na 2 WO 4 is added in an aqueous solution at 0.1-3% molar and then a solution of 35% hydrogen peroxide 1.0-1.3 eq. at temperatures from 50° C. to 85° C. is slowly added; reduction of the 4-nitro-4′-amino-diphenyl-sulfone by hydrogenation in the presence of a Pd/C or Pt/C catalyst obtaining the 4-4′-diamino-diphenyl-sulfone.