Persulfoxide: key intermediate in reactions of singlet oxygen with sulfides.

Persulfoxide (R(2)S(+)-OO(-) <--> R(2)S(.)-OO(.)) is the first formed intermediate in the reactions between singlet oxygen and organic sulfides. It is a weakly bound species that nevertheless has a sufficient lifetime to undergo a myriad of inter- and intramolecular reactions. Its behavior suggests that it can be considered as a resonance hybrid of zwitterionic and diradical canonical structures. It primarily acts as a nucleophile/base at oxygen but has a tendency to interconvert to secondary intermediates that often behave as electrophilic oxidizing agents. Judicious selection of reaction conditions and substituents can allow the use of the persulfoxide as a synthetically useful intermediate.