Chapter 7: Organosulfur Compounds in Organic Synthesis

Sulfur-containing functional groups including thiols, sulfides, sulfoxides, and sulfones are examined for their nucleophilic character and electron-rich nature, which makes them valuable reactants and intermediates. The chapter details the formation and reactivity of sulfonium and sulfoxonium ylides, species that facilitate carbon-carbon bond formation through mechanisms exemplified by the Corey-Chaykovsky reaction, an important strategy for constructing epoxide rings and cyclopropanes with defined stereochemistry. Oxidation and reduction processes involving sulfur compounds receive substantial attention, particularly the Swern oxidation, which allows selective conversion of alcohols to carbonyl compounds under mild conditions while maintaining stereochemical integrity. Sulfoxide chemistry is highlighted for its application in stereoselective transformations that exploit the configurationally stable sulfur center to direct bond formation with high selectivity. The chapter discusses sulfonate esters as exceptionally effective leaving groups in nucleophilic substitution and elimination reactions, properties that make them indispensable in constructing new carbon-heteroatom and carbon-carbon bonds. Sulfonyl chlorides and sulfonamides are presented within the context of protective group chemistry, demonstrating how sulfur-based functional groups can be installed and removed strategically to control reaction sequences. Throughout, reaction mechanisms are explained with emphasis on how sulfur's polarizability and orbital accessibility enable unprecedented selectivity and reactivity patterns that would be difficult to achieve with conventional carbon or oxygen-based reagents.