Structure and Reactivity of Amphoteric Oxygen Species

The structure and chemical properties of 1,3-dipolar peroxidic species (X+-O-O-) such as ozone (X = O), nitroso oxides or nitrenium peroxides (X = RN), carbonyl oxides or carbenium peroxides (X = R2C), and persulfoxides or sulfonium peroxides (X = R2S) have been attracting much attention from synthetic, biological, and theoretical standpoints. These active oxygen species can be classified into two types depending on whether the X+ is an enium (carbenium, nitrenium, silylenium etc.) ion or an onium (ammonium, oxonium, phosphonium, sulfonium etc.) ion, and their reactivities are quite different depending on the nature of X. The individual features as well as the overviews of structure and reactivities of these X-O-O species are reviewed. Ozone and nitroso oxides have an electrophilic character while carbonyl oxides usually act as a nucleophilic oxygen transfer agent, their reactivities being controlled by substituents. It is important to see whether or not XOO species can isomerize to the cyclic isomers. Al...