Oxidations Catalyzed By Seleninic Acids and Anhydrides, Their Precursors and Congeners

Background: Benzeneseleninic acid and anhydride are useful oxidants with numerous unique synthetic applications. They can be generated in situ from the oxidation of diphenyl diselenide with reagents such as hydogen peroxide, t-butyl hydroperoxide and ozone. In early work, stoichiometric amounts of the selenium reagent were typically employed, resulting in higher cost, more waste byproducts and occasionally complications from the further reactions of desired products with reduced selenium species. Methods: More recently, it has been demonstrated that catalytic amounts of the selenium compounds, often as low as 1 mol %, suffice for the required oxidations, provided that stoichiometric amounts of a co-oxidant such as hydrogen peroxide are present to regenerate the active selenium catalyst. Hydrogen peroxide is an environmentally benign oxidant that produces only water as a waste byproduct and can be employed in aqueous media. Results: Furthermore, appropriately substituted seleninic acids, anhydrides and their precursor diselenides afford improved catalytic activity and facilitate separation of the catalysts from the desired products. Conclusions: This review briefly summarizes the types of classical transformations effected by stoichiometric amounts of seleninic acid oxidants and their congeners, and then provides a survey of more modern catalytic variations, including the use of designer compounds that provide the means for greener reactions with improved efficiency and less waste.