Photochemical carbon–sulfur bond cleavage in some alkyl and benzyl sulfides

Irradiation (254 nm) of five alkyl and benzyl ethyl sulfides causes efficient (Φr 0.27–0.90) homolytic cleavage of the C–S bond. Of the resulting fragments, thiyl radicals mainly couple, while alkyl radicals abstract hydrogen, disproportionate or couple when stabilized (benzyl). Selective trapping of either of the two types of radicals occurs in the presence of nucleophilic (methyl vinyl ether and 1-hexene) and, respectively, electrophilic (acrylonitrile) alkenes. When an easily oxidized radical is formed, e.g. cumyl, secondary electron transfer leads to the corresponding cation.