text: Arylsulfonyl chlorides are made industrially in a two-step, one-pot reaction from an arene (in this case, benzene) and chlorosulfuric acid:
  The intermediate benzenesulfonic acid can be chlorinated with thionyl chloride as well. Benzenesulfonyl chloride, the most important sulfonyl halide, can also be produced by treating sodium benzenesulfonate with phosphorus pentachlorides.
  Benzenediazonium chloride reacts with sulfur dioxide and hydrochloric acid to give the sulfonyl chloride:
  For alkylsulfonyl chlorides, one synthetic procedure is the Reed reaction: