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Abstract
Iodosobenzene diacetate has chemical, electrochemical, and physical properties that make its use attractive in both chemical and electrochemical reactions. It is a powerful two-electron oxidant that can be made from iodobenzene electrochemically and that can be used in a number of useful organic oxidations, in particular the oxidative rearrangement of amides. In this study iodosobenzene diacetate was prepared chemically by the reaction of iodobenzene with a mixture of hydrogen peroxide and acetic anhydride. Iodosobenzene diacetate was also prepared electrochemically by the anodic oxidation of iodobenzene in a mixture of acetic acid, methanol, and sodium acetate. A cyclic voltammetric study of nine iodosobenzene biscarboxylates showed a linear relationship between the half-peak potential and Taft's inductive parameter (sigma)(,I). Electron-withdrawing substitutents in the carboxylate moiety were found to decrease the reduction potential (compared to iodosobenzene diacetate) and to increase the oxidizing power of the reagent. Electron-releasing substituents were found to have the opposite effect. A combined electrochemical and chemical oxidation of nine primary carboxamides in which iodobenzene functioned as a "catalyst" were carried out in a mixture of acetic acid and methanol (with sodium acetate as supporting electrolyte). The methyl carbamates resulting from the oxidative rearrangement of the amides (a reaction shown not to proceed electrochemically under these conditions) were formed in 3-41% yields, based on nmr analysis. These results are suggestive of a cyclic (catalytic) process but do not require such a process.
