Oxidative Coupling with S-N Bond Formation

Oxidative strategies are a powerful tool in organic synthesis for the formation of heteroatom-heteroatom, carbon-heteroatom, and carbon-carbon bonds. Among these processes the reactions of oxidative S-N bond formation deserve considerable interest as convenient, effective, and environmentally friendly alternatives to existing methods for the synthesis of a great variety of organic compounds widely used in organic and medicinal chemistry. These transformations take place through the interaction of S- and N-reagents and an oxidant, by radical or ionic mechanisms. Sulfinic acids and their salts, thiols, sulfonyl hydrazides, and thiosulfonates are generally used as S-reagents; aliphatic and aromatic amines are usually applied as N-reagents. The role of the oxidant mostly lies in the oxidation of the S-reagent, after which the formed active species reacts with the N-reagent to result in the S-N coupling product. There are two versions of oxidative S-N coupling processes: the intermolecular variant opens simple pathways to sulfen-, sulfin-, and sulfonamides, sulfenyl- and sulfoximines, sulfanes, and sulfur diimides, whereas the intramolecular one leads to the formation of various heterocycles. Of the major problems associated with successful performance of oxidative S-N coupling reactions, the first relates to the search for coupling partners that will work together to form a new bond under oxidative conditions. The second is the choice of a suitable oxidative system that will not overoxidize starting compounds. That is why mild oxidants, such as hypervalent iodine compounds and copper salts and complexes, are generally applied in these processes. This is the first exhaustive review relating to achievements in oxidative transformations involving S-N bond formation. It summarizes 134 references, mainly from 2000 to 2018, and is divided into chapters according to the classes of compounds synthesized.