Photooxidation of alkyl 4-nitrophenyl sulfides and sulfoxides. Observation of oxidative C-S bond cleavage and rearrangement reactions

Article abstract of DOI:10.1021/ja00099a015

Alkyl 4-nitrophenyl sulfides and sulfoxides undergo a self-photoinduced, singlet oxygen oxidation to produce a variety of products, including sulfonates and carbonyl compounds formed by the oxidative cleavage of the C-S bond of the sulfides and sulfoxides. Structural rearrangements are observed in the resulting carbonyl compounds formed in the oxidative cleavage of the C-S bond in the tert-amyl and 2-phenylethyl sulfides. An overall mechanism is proposed which involves the formation of peroxysulfoxides and peroxysulfones which undergo heterolytic C-S bond cleavage to form ion pairs which recombine to form persulfenates or persulfinates which then undergo photo- and/or thermallyinduced homolytic O-O bond cleavage to form alkoxy and sulfinyl or sulfonyl radicals. The alkoxy radicals undergo β-scission, disproportionation, or recombination with the sulfonyl radical to form the observed products. These C-S oxidative cleavage reactions have only been rarely observed in the earlier studies on the singlet oxygen oxidation studies of dialkyl sulfides, and are attributed, in part, to the presence of the 4-nitro group on the aromatic ring which greatly affects the susceptibility of the sulfur atom of the sulfides and sulfoxides toward nucleophilic attack, and on the reactivity of the peroxysulfoxides and peroxysulfones toward heterolytic cleavage of the O-S bond.