Pauson-Khand Reactions of Alkenyl Sulfones and Alkenyl Sulfoxides: Applications in Asymmetric Synthesis

Unlike other types of electron-deficient alkenes, alkenyl sulfones and alkenyl sulfoxides are excellent alkene partners in Pauson-Khand reactions (PKR). In the case of the intramolecular PKR of appropriately substituted 1-sulfinyl-1,6-enynes and 1-sulfonyl-3-oxygenated-1,6-enynes novel stereoselective processes and applications in asymmetric synthesis have been developed. Furthermore, using the cobalt-chelating dimethylaminophenyl vinyl sulfoxide as substrate, their intermolecular PKR with terminal alkynes provide the first intermolecular asymmetric version of PKR with non-strained alkenes. The resulting 5sulfinyl-2-cyclopentenones are versatile intermediates in the enantioselective synthesis of natural cyclopentanoids. 1 Introduction 2 Background: PKR of Electron-Deficient Alkenes 3 Intramolecular PKR of (gamma)-Oxygenated (alpha),(beta)-Unsaturated ­Sulfones and Related Enynes 4 PKR of (alpha),(beta)-Unsaturated Sulfoxides 4.1 Intramolecular Processes 4.2 Intermolecular Processes 4.3 Applications to the Enantioselective Synthesis of Natural Cyclopentanoids 5 Summary