Over the past few years, CuH-catalyzed hydroamination has been discovered and developed as a robust and conceptually novel approach for the synthesis of enantioenriched secondary and tertiary amines. The success in this area of research was made possible through the large body of precedent in copper(I) hydride catalysis and the well-explored use of hydroxylamine esters as electrophilic amine sources in related copper-catalyzed processes. This Minireview details the background, advances, and mechanistic investigations in CuH-catalyzed hydroamination.

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Copper Hydride Catalyzed Hydroamination of Alkenes and Alkynes

Coordination chemistry of metal alkynyl compounds

The reduction of diverse functional groups is an essential protocol in organic chemistry. Transition-metal catalysis has been successfully applied to the reduction of olefins, alkynes, and many carbonyl compounds via hydrogenation or hydrosilylation; the latter presenting several advantages over hydrogenation. Notably, hydrosilylation generally occurs under mild reaction conditions, and consequently over-reduced products are rarely detected. Moreover, the great majority of hydrosilanes employed in this reaction are easily handled, inexpensive, or both. A large number of multiple bonds can be involved in this context, and the hydrosilylation reaction can be regarded as a useful method for the synthesis of silicon-containing organic molecules or a convenient way of reducing organic compounds. Furthermore, the silyl group can also be retained as a protecting group, a strategy that can be of great usefulness in organic synthesis. Since the first Wilkinson's catalyst-mediated hydrosilylation of ketones in 1972, metals such as rhodium and iridium have attracted most of the attention in this area. A wide array of catalytic systems for hydrosilylation reactions is nowadays available, which has allowed for a great expansion of the synthetic scope of this transformation. After having been overlooked in the early years, group 11 metals (Cu, Ag, and Au), especially copper, have emerged as appealing alternatives for hydrosilylation. The use of a stabilized form of copper hydride, the hexameric [(Ph3P)CuH]6, by Stryker represented a breakthrough in copper-catalyzed reduction reactions. Nowadays, several copper-based catalytic systems compare well with a variety of reported rhodium-based catalysts, which generally suffer from the high cost of the catalyst. Tertiary phosphine ligands are the most widely used in these transformations. However, other families such as N-heterocyclic carbenes (NHCs) have shown promising activities. Compared with copper, little attention has been paid to silver- or gold-based catalysts. Silver salts have been considered inert towards hydrosilylation, and they are often employed as innocent anion exchange reagents for the in situ generation of cationic transition metal catalysts. Despite the rare reports available, they have already shown interesting reactivity profiles, for example, in the chemoselective reduction of aldehydes in the presence of ketones. Furthermore, 1,2-hydride delivery is favored over 1,4-reductions for alpha,beta-unsaturated carbonyl compounds, in contrast with most copper-based systems.

Copper, silver, and gold complexes in hydrosilylation reactions.

Hydride complexes of copper, silver, and gold encompass a broad array of structures, and their distinctive reactivity has enabled dramatic recent advances in synthesis and catalysis. This Review summarizes the synthesis, characterization, and key stoichiometric reactions of isolable or observable coinage metal hydrides. It discusses catalytic processes in which coinage metal hydrides are known or probable intermediates, and presents mechanistic studies of selected catalytic reactions. The purpose of this Review is to convey how developments in coinage metal hydride chemistry have led to new organic transformations, and how developments in catalysis have in turn inspired the synthesis of reactive new complexes.

Coinage Metal Hydrides: Synthesis, Characterization, and Reactivity.

The chemistry of higher order organocuprates

Preparation and crystallographic characterization of a hexameric triphenylphosphinecopper hydride cluster

Synthesis and molecular geometry of hexameric triphenylphosphinocopper(I) hydride and the crystal structure of H6Cu6(PPh3)6. HCONMe2 [hexameric triphenylphosphino copper(I) hydride dimethylformamide]

Crystal and molecular structure of bis(triphenylphosphine)octakis(phenylethynyl)tetracopperdiiridium(4 Cu-Cu) (8 Cu-Ir), novel heteronuclear octahedral metal cluster complex

X-ray crystallographic studies on fluxional pentacoordinate transition metal complexes. III. (Cycloocta-1,5-diene)[bis(1,3-diphenylphosphino)propane]methyliridium(I)

X-ray crystallographic studies on fluxional pentaccordinate transition metal complexes. I. (Cycloocta-1,5-diene)bis(dimethylphenylphosphino)methyliridium(I)

Susan A. Bezman

Papers

Preparation and crystallographic characterization of a hexameric triphenylphosphinecopper hydride cluster

Synthesis and molecular geometry of hexameric triphenylphosphinocopper(I) hydride and the crystal structure of H6Cu6(PPh3)6. HCONMe2 [hexameric triphenylphosphino copper(I) hydride dimethylformamide]

Crystal and molecular structure of bis(triphenylphosphine)octakis(phenylethynyl)tetracopperdiiridium(4 Cu-Cu) (8 Cu-Ir), novel heteronuclear octahedral metal cluster complex

X-ray crystallographic studies on fluxional pentacoordinate transition metal complexes. III. (Cycloocta-1,5-diene)[bis(1,3-diphenylphosphino)propane]methyliridium(I)

X-ray crystallographic studies on fluxional pentaccordinate transition metal complexes. I. (Cycloocta-1,5-diene)bis(dimethylphenylphosphino)methyliridium(I)