Neighboring-Group Participation in Organic Redox Reactions: Effect of Tertiary Amine and Pyridine Groups on the Kinetics and Mechanism of Thioether-Sulfoxide Interconversions

Article abstract of DOI:10.1021/jo00320a002

The effect of neighboring tertiary amine, quaternary ammonium, and pyridine substitution on both the oxidation of thioethers by aqueous I2 and the reduction of sulfoxides by aqueous HI has been evaluated.The millionfold acceleration in the rates of the reaction of 5-methyl-1-thia-5-azacyclooctane and its sulfoxide is unique.The rates of the lower homologues and cyclic analogues are not accelerated and at a given acid concentration the rates of oxidation of amine sulfides follow the rate law d/dt=-k_ox^-1.The rates of reduction of the aminesulfoxides follow the rate law d/dt=k_red.The pH profiles of the I2 oxidation of 6-methyl-2-thia-6-azaheptane and 2-<2-(methylthio)ethyl>pyridine demonstrate neighboring-group participation and suggest N-S interacted intermediates.