Takeo Miyazawa

Application of redox system based on nitroxides to organic synthesis

Tetramethylpiperidine-l-oxyl kno,wn as a stable r adical is reduced to the hydroxylamine and is also oxidized to the oxoaminium ion. These redox reactions a re chemically reversible. In this review. some applications of nitroxyl radical to organic reactions based on its redox function were described. The hydroxylamine was demonstrated to work as a hydration reagent of nitriles to produce amides. Further, it was found that oxygen is reduced by an anion of hydroxylamine to give superoxide ion. The oxoaminium salt could selectively oxidized hydroxide ion and alcohols to hydrogen peroxide and the corresponding carbonyl compounds, respectively. Furthermore hydroxyl groups of poly(viny1 alcohol )s were partially oxidized to carbonyl groups. The redox systems using oxoaminium salt as a mediator were investigated, and it was found that the polymeric mediator was superior to the corresponding monomeric mediator. oxidation of ester-containing alcohols. T hat is, whereas could little or not oxidize 2-benzoyloxyetha nol and 3-benzoyloxyprop anol, it did 4-benzoyloxybuta nol, 5- benzoyloxypentan ol, and S-benzoyloxyhexanol to the corresponding b enzoyloxyalkana ls. The origin of the selectivity might be attributed to the i nductive effect of the ester group. A new kind of selectivity was found in the