Process for producing diphenyl sulfone compound

The present invention is to provide methods for preparing a compound of Formula (I) (wherein, R 1 and R 2 are each independently halogen, alkyl having 1 to 8 carbons or alkenyl having 2 to 8 carbons; m and n are each independently 0 or an integer of 1 to 4; and R 3 is alkyl having 1 to 8 carbons, alkenyl having 2 to 8 carbons, cycloalkyl having 3 to 8 carbons or optionally substituted aralkyl) reacting a compound of Formula (II) (wherein R 1 and R 2 , m and n are as defined above) with a compound of Formula (III) €ƒ€ƒ€ƒ€ƒ€ƒ€ƒ€ƒ€ƒR 3 -X€ƒ€ƒ€ƒ€ƒ€ƒ(III) (wherein R 3 is as defined above and X is halogen) in a solvent in the presence of a base and the compound of Formula (III) is (1) removed from the reaction mixture, (2) present in the reaction in 5 % by weight or less in the purification process or (3) removed by distillation. Additionally, the invention provides methods for preparing a compound of Formula (I) such that (4) the reaction process is carried out in a solvent containing 0.05 ppm or less of iron components, (5) the purification process is carried out in water containing 0.05 ppm or less of iron components, (6) the reaction process is carried out in a tank with a corrosion-resistant layer over the inner wall, (7) the purification process is carried out in a tank with a corrosion-resistant layer over the inner wall, (8) a chelating agent is added to the purification process or (9) the product is dried with mechanical stirring.