α-Hydroxy Hydroperoxides (Perhydrates) as Oxygen Transfer Agents in Organic Synthesis

This review deals with general methods of preparation of α-hydroxy hydroperoxides and their application in the oxidation of organic compounds. The article covers the literature through 1994. In this article, the scope of application of the α-hydroxy hydroperoxides is limited to their role as oxygen transfer agents in the oxidation of organic compounds. α-Hydroxy hydroperoxides, generated from a ketone and hydrogen peroxide, possess an activated oxygen atom which is easily transferred to a variety of organic compounds. The reagent can oxidize olefins to epoxides, aldehydes to carboxylic acids, ketones to esters (Baeyer-Villiger reaction), arenes to phenols or quinones and sulfides and amines to their oxides. Many of these oxidations are performed with hydrogen peroxide and catalytic quantities of the ketone through the intermediary ketone hydrate. This represents one of the few examples of catalytic hydrogen peroxide activation without metal ions. The preparation and properties of the important 2-hydroperoxyhexafluoropropan-2-ol are discussed in detail. The α-hydroxy hydroperoxides offer an interesting reagent of synthetic utility in the laboratory and in industry. Their regio- and stereoselectivities exhibited in many reactions are remarkable. The requirement of this reagent in catalytic quantities and availability of the precursor ketones on commercial scale, such as hexafluoroacetone, furthers the incentive for research in this area. Oxidation of 2-methylnaphthalene directly to 2-methyl-1,4-naphthoquinone (vitamin K₃) with aqueous hydrogen peroxide catalyzed by hexafluoroacetone emphasizes the potentials of this system for industrial applications. The review highlights these and other synthetic potentials of these reagents with a view to furthering the developments in the oxidation of organic compounds.

The catalytic oxidation of organic compounds by the ketone/H₂O₂ system.