Scope and Limitations of Xanthate-Mediated Synthesis of Functional γ-Thiolactones

A modular platform based on free-radical xanthate addition to alkenes enables access to a large series of functional γ-thiolactones. This methodology includes two different pathways based on xanthate chemistry involving radical addition and Chugaev elimination steps. The first method uses the addition of an ester-functionalized xanthate to various commercially functional alkenes, whereas the second one is based on the addition of functional xanthates to an ester-functionalized alkene. In both cases, a series of xanthate/alkene monoadducts was obtained, and their thermolysis and subsequent cyclization led to a library of functional γ-thiolactones in moderate to good yield. For a few cases where it may not be possible to directly incorporate some targeted functional groups via the proposed process involving free radicals and high temperature, a bromo-functionalized thiolactone was used as a starting material for chemical transformations.