Rhodium- and Iridium-Catalyzed Hydroamination of Alkenes

The hydroamination of alkenes represents an atom-economical strategy for the synthesis of nitrogen-containing molecules from readily available components. In recent years, the application of Group 9 transition metal catalysts in this reaction has enabled significant progress to be made toward addressing several major challenges within the field of metal-mediated hydroamination. Using Rh- and Ir-based catalysts for the intermolecular hydroamination reaction, advances have been made in the regioselective addition of amines to olefins in an anti-Markovnikov fashion producing industrially relevant linear amine products, as well as the concise synthesis of chiral amines by asymmetric hydroamination. The intramolecular addition of a variety of amine groups to pendant alkenes has also been studied in the context of developing expedient routes to nitrogen-containing heterocycles; using simple Rh- and Ir-based catalysts, a wide range of substrates including those that contain functional groups that are poised for further synthetic elaboration are readily cyclized. Extension of these catalyst systems to include the asymmetric synthesis of a variety of functionalized 1-methylpyrrolidine compounds has recently been achieved. To complement these catalytic investigations, thorough stoichiometric and kinetic studies have unveiled diverse mechanistic pathways that originate from either initial amine or olefin activation. The understanding gained through these mechanistic investigations provides the framework for the design of increasingly effective alkene hydroamination catalysts.