THE OXIDATION OF ALCOHOLS BY PERMANGANATE - A COMPARISON WITH OTHER HIGH-VALENT TRANSITION-METAL OXIDANTS

The results obtained from a study of the oxidation of mandelic acid and cyclobutanol by permanganate in 1.0 M KOH are best accommodated by a mechanism in which the initial reaction is the addition of a manganese-oxo bond to the alpha-C-H bond of the alcohol, followed by homolytic cleavage of the resulting Mn-C bond to give free-radical intermediates. A comparison with other high-valent transition-metal oxidants suggests that it is possible to systematically classify the way in which these reagents react with alcohols on the basis of the initial reaction (C-H or O-H addition) and the cleavage mode of the metal-oxygen or metal-carbon bond (homolytic or heterolytic). The approach provides a framework for understanding these reactions that is less chaotic than the current situation where distinctive mechanisms have been proposed for each individual oxidant.