Pro-oxidant action of sulfur compounds : Catalysis of autoxidation by onium salts

It is shown that the initiation of the autoxidation of cumene by triphenylsulfonium salts is due not to oxygen activation, as stated in the literature, but to a sulfonium-catalysed homolytic cleavage of cumene hydroperoxide. The activity of triphenylsulfonium chloride is considerably enhanced by addition of solid calcium carbonate, which effect is attributed to the removal of chloride ions. In keeping with this, triphenylsulfonium hydroxide was found to display an even higher activity.