Preparation and Reactivity of Organomanganese Compounds

Abstract

Abstract This chapter deals with the preparation of organomanganese reagents from organolithium or organomagnesium compounds (transmetallation) as well as from organic halides and manganese metal (oxidative addition). The influence of various parameters on the stability of organomanganese reagents is then discussed (nature of the reagent RMnX, R 2 Mn, R 3 MnLI or R 3 MnMgX; effect of ligands and solvents…). The second part of the chapter is devoted to the reactivity of these reagents and to their uses in organic synthesis. They are especially interesting for their chemoselectivity, as illustracted by the addition to aldehydes and ketones, the preparation of ketones by acylation or the copper‐catalyzed conjugate addition to enones, enals and enoates. Organomanganese reagents can also be used to perform various iron, palladium or nickel‐catalyzed cross‐coupling reactions. Manganese salts are efficient catalyst to achieve various homo‐ and heterocoupling reactions using Grignard reagents. They are also used to catalyze the addition of Grignard reagents to acetylenes, 1,3‐dienes and allenes. Finally, various radical cyclization reactions promoted by organomanganates are presented.