Manganese(III) Acetate: A Versatile Reagent in Organic Chemistry

Abstract

Free radical reactions have become increasingly important, as well as a very attractive tool, in organic synthesis within the last two decades, due to their powerful, selective, specific, and mild reaction abilities. Mn(OAc)3 mediated oxidative free radical reactions have been extensively developed in the last twenty years. Numerous regio-, chemo-, and stereoselective synthetic methods have been developed in both inter- and intramolecular reactions, and have detailed the progress of Mn(OAc)3 mediated oxidative free radical reactions since the end of the 19th century. The new literature about the new synthetic methods on Mn(OAc)3 mediated carbon-carbon bond formation and carbon-oxygen bond formation reactions has not been extensively reviewed. The present paper summarizes the recent developments in oxidative free radical reactions mediated by Mn(OAc)3. Mn(OAc)3 mediated reactions of conjugated systems (e.g., alkenes, alkynes, 1,3-alkadienes, l,3-alkadiynes, 1-alken-3-ynes) with β-dicarbonyl compounds, Mn(OAc)3 mediated alkylation, such as the oxidative addition of an aldehyde or ketone to alkenes, Mn(OAc)3 mediated free-radical cyclization of alkenes with active methylene compounds in the presence of oxygen to afford the cyclic peroxides; lactone synthesis by the Mn(OAc)3 mediated oxidative addition of carboxylic acids to alkenes, Mn(OAc)3 mediated cyclization of α- (methylthio)acetamides, enamides, and β-keto carboxamides to afford cyclic products. Mn(OAc)3 oxidative free-radical cyclizations of allylic β-dicarbonyl compounds, for example, the cyclization of allylic β-ketoesters to afford the corresponding γ-lactone. The reaction of alkenes with sodium azide in the presence of acetic acid was investigated to Keywords: Free radical reactions, Lactone synthesis, Cycloperoxidation, Oxidative Cyclization, Carbon-Oxygen Bond Formation