Neighboring-Group Participation in Organic Redox Reactions. 10. The Kinetic and Mechanistic Effects of Imidazole and Benzimidazole Nitrogen on Thioether Oxidations

Article abstract of DOI:10.1021/jo00201a002

The kinetics of the aqueous iodine oxidation of a number of imidazolyl- and benzimidazolylalkyl methyl sulfides have been studied.Evidence of neighboring-group participation has been observed in all cases.The anchimeric assistance provided by the benzimidazole moiety is evidenced by rate accelerations of 10²-10⁵.The oxidation of 1-methyl-2-<3-(methylthio)propyl>imidazole, 1, is 10⁶ times faster than that of simple thioethers and is faster than any previously reported acyclic thioether.The reaction of 2-<3-(methylthio)propyl>benzimidazole is accelerated by10⁵ via a transient N-S dication.Additionally, the pH profiles of all of the compounds studied provide strong evidence for N-S interacted intermediates.