Kai C. Hultzsch

Hydroamination: Direct Addition of Amines to Alkenes and Alkynes

8.4.5. Nitromercuration Reactions 3878 9. Hydroamination of Alkenes and Alkynes under Microwave Irradiation 3878 * To whom correspondence should be addressed. Phone: +49 241 8

Catalytic asymmetric hydroamination of non-activated olefins

Hydroamination is a highly atom-economical process in which an amine N-H functionality is added to an unsaturated carbon-carbon linkage. This potentially highly useful process gives access to various nitrogen-containing basic and fine chemicals as well as naturally occurring alkaloid skeletons. Asymmetric hydroamination reactions promoted by chiral catalysts are particularly attractive. This review highlights recent progress in the development of early transition metal catalysts for the asymmetric hydroamination of non-activated alkenes.

Base-catalysed asymmetric hydroamination/cyclisation of aminoalkenes utilising a dimeric chiral diamidobinaphthyl dilithium salt

A dimeric proline derived diamidobinaphthyl dilithium salt represents the first example of a chiral main group metal based catalyst for asymmetric hydroamination/cyclisation reactions of aminoalkenes.

Half‐Sandwich Alkyl and Hydrido Complexes of Yttrium: Convenient Synthesis and Polymerization Catalysis of Polar Monomers

Direct preparation of alkyl half-sandwich complexes of the heavier rare earth elements (such as 1) is possible by alkane elimination from the corresponding cyclopentadiene derivative and the trialkyl complex [Y(CH2SiMe3)3(thf)2]. Hydrogenation of 1 gives the highly fluxional dimeric hydride complex 2. Both complexes catalyze the polymerization of the polar monomers tert-butyl acrylate and acrylonitrile.

Kinetic resolution of chiral aminoalkenes via asymmetric hydroamination/cyclisation using binaphtholate yttrium complexesElectronic supplementary information (ESI) available: experimental procedures and characterising data for all new complexes and substrates. See http://www.rsc.org/suppdata/cc/b3/b316096c/

Chiral binaphtholate yttrium aryl complexes are highly active and enantioselective catalysts for the asymmetric hydroamination of aminoalkenes, as well as the kinetic resolution of alpha-substituted 1-aminopent-4-enes to give trans-2,5-disubstituted pyrrolidines with good enantiomeric excess and high k(rel).

The mechanism of hydroaminoalkylation catalyzed by group 5 metal binaphtholate complexes.

The intermolecular hydroaminoalkylation of unactivated alkenes and vinyl arenes with secondary amines occurs readily in the presence of tantalum and niobium binaphtholate catalysts with high regio- and enantioselectivity (up to 98% ee). Mechanistic studies have been conducted in order to determine the kinetic order of the reaction in all reagents and elucidate the rate- and stereodetermining steps. The effects of substrate steric and electronic properties on the overall reaction rate have been evaluated. The reaction is first order in amine and the catalyst, while exhibiting saturation in alkene at high alkene concentration. Unproductive reaction events including reversible amine binding and arene C-H activation have been observed. The formation of the metallaaziridine is a fast reversible nondissociative process and the overall reaction rate is limited either by amide exchange or alkene insertion, as supported by reaction kinetics, kinetic isotope effects, and isotopic labeling studies. These results suggest that the catalytic activity can be enhanced by employing a more electron-deficient ligand backbone.

Early Transition Metal (Group 3–5, Lanthanides and Actinides) and Main Group Metal (Group 1, 2, and 13) Catalyzed Hydroamination

The hydroamination of alkenes, dienes, allenes, and alkynes by early transition metal catalysts has seen significant progress over the last decade, especially with respect to control of regio- and stereoselectivity and the synthesis of more complex nitrogen-containing skeletons. This article provides an overview over the application of catalyst systems based on the 17 rare earth elements, as well as group 4 and group 5 metals. These electropositive metal catalysts operate via activation of the amine to form catalytic active metal-amido or metal-imido species, although the true nature of this species is not known with certainty for all systems and may vary for different substrate classes. This mode of activation differentiates early transition metal catalysts from many late transition metal catalysts that operate via activation of the unsaturated C–C linkage (alkene, 1,3-diene, allene, or alkyne). Alkali metals, alkaline earth metals and aluminum are included in this overview as well, as they show strong similarities in their reactivity and mechanistic pathways to aforementioned early transition metals. While the structure-reactivity principles are well understood for certain hydroamination processes, e.g., in the intramolecular hydroamination of aminoalkenes or the intermolecular hydroamination of alkynes, other transformations, in particular the intermolecular hydroamination of alkenes, remain highly challenging. Due to the potential of the hydroamination process for the synthesis of pharmaceuticals and other industrially relevant fine chemicals, a strong emphasis is given on the application of chiral catalysts in stereoselective processes.

Halbsandwich-Alkyl- und Hydridoyttriumkomplexe: einfache Synthese und Polymerisationskatalyse polarer Monomere

Ganz direkt lassen sich Alkyl-Halbsandwichkomplexe der schwereren Seltenerdelemente wie 1 durch Alkaneliminierung aus dem entsprechenden Cyclopentadien und dem Trialkylkomplex [Y(CH2SiMe3)3(thf)2] herstellen. Die Hydrierung von 1 liefert den stark fluktuierenden dimeren Hydridokomplex 2. Beide Komplexe katalysieren die Polymerisation der polaren Monomere tert-Butylacrylat und Acrylnitril.

Catalytic σ-Bond Metathesis

This account summarizes information on recently reported applications of organo-rare-earth metal complexes in various catalytic transformations of small molecules. The σ-bond metathesis at d0rare-earth metal centers plays a pivotal role in carbon–carbon and carbon–heteroatom bond forming processes. Relevant mechanistic details are discussed and the focus of the review lies in practical applications of organo-rare-earth metal complexes.

Synthesis and structural characterisation of novel linked bis(β-diketiminato) rare earth metal complexes

Rare earth metal complexes based on novel linked bis(beta-diketiminato) ligands have been prepared via amine elimination and their structural characterisation revealed that the linker unit has significant influence on the geometry and coordination mode of the ancillary ligand.