Preparation and Reactions of Unsymmetrically Labeled Hydroperoxides: Solvent Viscosity Dependent Oxygen Scrambling of Cumylperoxyl Free Radicals

摘要

Hydroperoxides are the principal products formed in the free radical oxidation of organic compounds including items of commerce and biologically important molecules, and they are also important oxidants in synthetically useful transformations such as the Sharpless epoxidation. Mechanistic studies have provided a basic understanding of autoxidation and other synthetically useful oxidation processes involving hydroperoxides, but many questions remain unanswered. One example of such an unresolved question concerns whether the proximal or terminal oxygen is transferred in the simplest reactions of hydroperoxides, i.e., with phosphines and sulfides, as well as in the Sharpless epoxidation. While important information has been obtained utilizing labeled molecular oxygen or randomly labeled hydroperoxides, unsymmetrically labeled hydroperoxides or peroxyl radicals have not been utilized in mechanistic studies, despite the fact that these compounds could provide decisive information about the chemistry of hydroperoxides and peroxyl free radicals. We report here the synthesis and study of two hydroperoxides labeled with ~(18)O exclusively at the terminal oxygen.