Sulfoxides and disulfides from sulfenic acids: Synthesis and applications

Sulfur-based functional groups are found in a broad range of natural products and therapeutic compounds. The sulfoxide moiety is present in a significant portion of pharmaceuticals, some of them already approved by the FDA, and plays an important role in the therapeutic effects. Sulfoxides are mainly obtained from the oxidation of sulfides but many of the oxidation methodologies suffer from synthetic disadvantages. The disulfide bond has a biological relevance in Nature processes, such as the structure stabilization and aggregation of proteins and can be considered a cleavable linker used in the controlled release of therapeutic drugs and pro-drugs in medicinal chemistry applications. Disulfides can be easily formed by the oxidation of two thiol groups or thiol-disulfide exchange reactions but preparation of non-symmetrical disulfide is not an easy task. The sulfenic acid function constitutes an unusual source of sulfoxides and disulfides, in reactions that almost always require only heating. This review covers the work that has been done on the synthesis of sulfoxides and disulfides via sulfenic acid intermediacy and the applications that this chemistry offers in the biological and medical field and in materials science.