The free-radical addition of thiophenol to bornylene and apobornylene: structures of product sulphides and sulphones formed on oxidation

Abstract

The free-radical addition of thiophenol to bornylene affords phenyl isobornyl sulphide and phenyl epi-isobornyl sulphide, the products of exo radical attack. Oxidation converts these sulphides into the corresponding exo-sulphones, which on treatment with potassium t-butoxide in t-butyl alcohol are epimerized to give the corresponding endo-sulphones, phenyl bornyl sulphone, and phenyl epibornyl sulphone. These results coupled with those on thiol addition to hexachloronorbornadiene, indicate that steric effects are not the sole factors controlling the direction of radical attack. The addition of thiophenol to camphene, in the presence of sulphuric acid and acetic acid, first performed by Posner, is shown to give phenyl isobornyl sulphide. The addition of thiophenol to apobornylene is analogous to the addition to bornylene, and affords the product of exo radical attack, phenyl iso-apobornyl sulphide, which on oxidation gives the corresponding exo-sulphone, epimerized to endo-sulphone in the presence of potassium t-butoxide in t-butyl alcohol.