Acetylen‐Gold‐Komplexe

Hüttel, Rudolf; Forkl, Hans

doi:10.1002/cber.19721050522

Cited by 39 publications

(17 citation statements)

References 13 publications

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“…Several examples for this -mode of co-ordination to both gold(I) and gold(III) are known in the literature (6,7,8), some examples have even been characterized by X-ray crystal structure analyses (9,10). Here the C-C-bond length increases from 1.19 Å, a normal value for an alkyne, to 1.26 Å.…”

Section: Theoretical Backgroundmentioning

confidence: 97%

Homogeneous gold catalysts and alkynes: A successful liaison

2003

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The use of the combination of homogeneous gold-catalysts and alkynes in organic synthesis is reviewed from its beginnings in C-N-bond formation to the newest developments in C-C-bond formation. The common basic principle of these reactions is discussed. Special attention is devoted to the question where the gold catalysts are superior to either other catalysts or more traditional synthetic approaches to the product molecules.Transition metal catalysis has become one of the most important tools in organic synthesis. It allowed entirely new transformations which were not possible previously by "traditional" organic reactions and thus significantly increased the efficiency of synthesis. It also made retrosynthetic analysis more demanding as many of the transformations go along with a remarkable increase in molecular complexity (1) which makes the relationship between the product and the starting material more difficult to recognize. In many of these reactions, especially in the case of late transition metals, C-C multiple bonds in either alkenes or alkynes, are the site of reaction. Theoretical backgroundIn the field of homogeneous gold catalysis the alkynes 1, which have the structural motive of a C-C-triple bond, belong to the most popular substrates. The reason for that popularity is the high reactivity of the alkynes which originates from their electronic structure (2). Often the corresponding alkenes with their C-C-double bond are less reactive.On one hand, the alkynes possess two orthogonal -orbitals high in energy occupied by two electrons each. These react with electrophilic reagents (E) like halogens in organic synthesis or electrophilic metal centers like gold (in the oxidation states I or III) in the field of transition metal catalysis (3,4). In the interaction with a metal center both the -orbital in the plane of metal co-ordination and theorbital perpendicular to it are able to interact with the dorbitals of the metal.On the other hand, the lowest unoccupied orbital of the alkynes is low in energy and thus eagerly react with strong nucleophiles like for example ethyne 2 with catalytical amounts of alkoholates in the Reppe synthesis of vinyl ethers 3 (5).Most unfortunately, weak nucleophiles (Nu) do not react directly with the alkynes, although this is often desired in organic synthesis. But the alkyne can be activated by co-ordination to the electrophilic gold complexes as mentioned above. This co-ordination withdraws electron

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Section: Theoretical Backgroundmentioning

confidence: 97%

Homogeneous gold catalysts and alkynes: A successful liaison

2003

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“…Early studies on reactions of acetylene derivatives with Gold(III) chloride report chlorination of the triple bond and reduction of at least some of the Au(III) to Au(I) [24]. A behavior also observed in the hydrochlorination of acetylene with several gold catalysts [25].…”

Section: >80% >90%mentioning

confidence: 97%

Homogeneous Gold Catalysis: Mechanism and Relativistic Effects of the Addition of Water to Propyne

et al. 2010

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Homogeneous catalysis employing gold compounds is a rapidly developing field. Au(III) catalysts in particular are interesting, since they exhibit catalytic properties unseen in other metals. In this study we report for the first time the complete mechanism of the nucleophilic addition of water to triple bonds that have not specifically been activated. The effect that the coordination of solvent molecules has on the course of the catalytic cycle is demonstrated, and the importance of hydrogen bonds to guide the substrate through the mechanism is highlighted. The influence of relativistic effects, which are particularly important for very heavy metals such as gold, is investigated, and it is concluded that the catalytic activity of gold could be seen as a relativistic effect.

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“…(41) Albeit no examples of a stable bicyclo[3.2.0]hept-5-ene obtained by a metal-catalyzed reaction from a 1,6-enyne have been observed, interestingly, following earlier work done with PtCl 2 as catalyst, 171 it was found that the goldcatalyzed reaction of 1,6-ene-ynamides gives cyclobutanones (equation 42), 172 in a process that probably proceeds through unstable bicyclic enamines. A remarkable cyclization of a 1,9-enyne (equation 43) to form a 10-membered ring has been disclosed.…”

Section: 170mentioning

confidence: 94%