text: In addition to the oxidation routes, diaryl sulfoxides can be prepared by two Friedel–Crafts arylations of sulfur dioxide using an acid catalyst:
  :2 ArH  +  SO   →  ArSO  +  HO
  Both aryl sulfinyl chlorides and diaryl sulfoxides can be also prepared from arenes through reaction with thionyl chloride in the presence of Lewis acid catalysts such as BiCl, Bi(OTf), LiClO, or NaClO.