Nucleophilie‐ und Elektrophilieskalen als Ordnungsprinzipien polarer organischer und metallorganischer Reaktionen

Mayr, Herbert; Patz, Matthias

doi:10.1002/ange.19941060905

Cited by 293 publications

(192 citation statements)

References 143 publications

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“…with anisole, for instance, is predicted from the tables of Mayr and Patz, [7] a reaction which was indeed observed experimentally. [13] For the rather electrophilic chloromethylene iminium salt (Vilsmeier-Haack ion) Mayr and Ofial [8] report an E parameter of -4.8, which indicates that this cation is about four times less reactive than the cumulene ion 1b ؉ .…”

Section: ⋅Kmentioning

confidence: 69%

“…For the comparison of electrophilic reactivities of different cations towards known nucleophiles the LFER lg k 20°C ϭ s (E ϩ N) developed by Mayr and Patz [7] has proven to be of great interpretive and predictive value. After extrapolation of the rate constant for the reaction of 1b ؉ ⋅CF 3 SO 3 -with 1,4-cyclohexadiene to 20°C from temperature dependent rate measurements (Arrhenius plot; activation parameters:…”

Section: Electrophilicity Parameters Ementioning

confidence: 99%

“…[7] From this relationship, it is possible to compare electrophiles of very different electrophilicity on a common reactivity scale. Fortunately, the rate constants for the reactions of classical iminium ions with several nucleophiles have recently been determined by Mayr and Ofial.…”

Section: Azaallylium Ionsmentioning

confidence: 99%

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Electrophilic Reactivity of a 2-Azaallenium and of a 2-Azaallylium Ion

Böttger

Fröhlich

Würthwein³

2000

Eur. J. Org. Chem.

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The rate constants for the reactions of the 2‐azaallenium ion 1b+, the 2‐azaallylium ion 2a+ and the iminium ion 3+ with different nucleophiles were determined by 1H NMR spectroscopy. By correlation with the Linear Free Enthalpy Relationship (LFER) lg k20°C = s (E + N), developed by Mayr and Patz, the electrophilicity parameters E(1b+) = ‐3.7, E(2a+) ≈︁ ‐16 and E(3+) = ‐10.43 were obtained. They show that the relative reactivities of these ions are approximately 1012:1:106. Quantum chemical calculations (ab initio, DFT) of the methyl anion affinities for the ions 1b+,2a+ and3+ are in agreement with the experimental E values. The X‐ray structure of 3+·CF3SO 3− is reported for the first time; it shows no strong interaction between the cation and the anion.

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Section: ⋅Kmentioning

confidence: 69%

Section: Electrophilicity Parameters Ementioning

confidence: 99%

See 1 more Smart Citation

Electrophilic Reactivity of a 2-Azaallenium and of a 2-Azaallylium Ion

Böttger

Fröhlich

Würthwein³

2000

Eur. J. Org. Chem.

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“…Die Rückreaktion mit der Geschwindigkeit v_, ist als termolekularer Prozeß kinetisch benachteiligt, so daß sie ausgeschlossen werden kann. 41 Weitere Experimente zur Transferhydrogenolyse ergaben, daß abgesehen von Triphenyl-, Diphenylfluormethan und Benzylfluorid auch 1-Adamantyl(diphenylmethyl)chlorid mit 9,10-Dihydroanthracen 2 unter H-Atom-Übertragung reagiert. Die Triebkraft der Transferhydrogenolyse mit Fluoriden beruht zweifellos auf der hohen Bindungsenthalpie von HF (136 kcal mol -1 der Literatur durch Studien zum Mechanismus überprüft und gestützt oder ergänzt werden.…”

Section: Transferhydrogenolyseunclassified

Nichtkatalysierte Transferhydrierung und Transferhydrogenolyse: neue Wege der Wasserstoffübertragung

1997

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Nichtkatalysierte Transferhydrierungen sind H2‐Übertragungsreaktionen von Donoren mit schwach gebundenen Wasserstoffatomen auf ungesättigte Acceptoren mit z. B. C‐C‐, C‐O‐, C‐N‐, N‐N‐oder N‐O‐Doppelbindungen, die durch H‐Atom‐Übertragung (Retrodisproportionierung) eingeleitet werden. Transferhydrogenolysen sind Reaktionen, bei denen σ‐Bindungen unter H2‐Addition gespalten werden. Die Hydrierungen werden durch eine H‐Übertragung abgeschlossen und folgen keinem Kettenmechanismus. Die einleitenden H‐Atom‐Übertragungsschritte beider Reaktionen ergänzen die bimolekularen Radikalbildungsreaktionen (Molecule Induced Radical Formation, MIRF) wie die Bildung von 1,4‐Diradikalen aus Alkenen oder Heteroalkenen. Transferhydrierung und ‐hydrogenolyse sind bei der Kohleverflüssigung ebenso von Bedeutung wie bei Aromatisierungen mit Nitroarenen oder Chinonen und möglicherweise sogar bei der biochemischen Dehydrierung. Wir berichten hier über Studien zum Mechanismus, über Struktur‐Reaktivitäts‐Beziehungen und die derzeitige Anwendungsbreite dieser Reaktionen.

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“…It has already been demonstrated that bicyclo [2,2,1]heptene (norbornene) is one of the most versatile model olefins in studies of the role of reagent structure of electron acceptor type E-L reagents on the course of the addition reaction. [1][2][3][4][5][6] From these studies, two types of information can be obtained: the structures of the products and their distribution inform us about the type of electron shift from the π electron system to acceptor E-L reagent;1-6 the relative rates of functionalisation of norbornene versus cyclohexene inform us about the geometry of the rate determining transition state, 7 being insensitive in the case of a three-centered intermediate (mercuric acetate 8 ), but very sensitive for four-centered or larger intermediates in (picryl azide 9 a rate ratio up to 8 .…”

Section: Introductionmentioning

confidence: 99%

The chemistry of organohalogenic molecules. Part 172. Kinetic studies of bromine transfer from N-bromo-succinimide to norbornene under protic conditions

Zupan¹,

Škulj²,

Stavber³

2002

Arkivoc

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Kinetic studies of bromofunctionalisation of cycloalkenes with N-bromosuccinimide (NBS) in acetonitrile-water under various conditions were carried out. Reaction with bicyclo[2,2,1]heptene (norbornene) in acetonitrile-water solution gave three main products: 2-exo-hydroxy-7-synbromo norbornane, 2-exo-hydroxy-7-anti-bromo norbornane and bromonortricyclane in 5:1:1 ratio. The course of the reaction obeys a simple rate equation:with k 2 = 0.35 M -1 s -1 at 10°C. In order to obtain further insight into the nature of the transition state during the bromine transfer from NBS, the effect of cycloalkene ring size was investigated and the following relative values were determined: 9.7 for the norbornene/cyclohexene pair, while a lower structural effect was found for the cyclopentene/cyclohexene pair, i.e. 1.2. For the bromination of norbornene the following activation parameters were determined: ∆H ‡ = 6.1 kcal mol -1 , ∆S ‡ = -38 cal mol -1 K -1 . The solvent polarity variation (Grunwald -Winstein Y) was used to obtain information about the nature of the rate determining step in bromine transfer from NBS to norbornene and m = 0.8 was determined, indicating a large change in the polarity of the transition state as compared to the reactants. The observed kinetic data suggests that the rate determining transition state in bromofunctionalisation of cyclic alkenes has a three-centered cyclic structure, the nucleophile also playing an important role.

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Nucleophilie‐ und Elektrophilieskalen als Ordnungsprinzipien polarer organischer und metallorganischer Reaktionen

Cited by 293 publications

References 143 publications

Electrophilic Reactivity of a 2-Azaallenium and of a 2-Azaallylium Ion

Electrophilic Reactivity of a 2-Azaallenium and of a 2-Azaallylium Ion

Nichtkatalysierte Transferhydrierung und Transferhydrogenolyse: neue Wege der Wasserstoffübertragung

The chemistry of organohalogenic molecules. Part 172. Kinetic studies of bromine transfer from N-bromo-succinimide to norbornene under protic conditions

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