Nucleophilicities and Lewis Basicities of Sterically Hindered Pyridines

Elsa Follet, Hendrik Zipse, Sami Lakhdar, Armin R. Ofial, Guillaume Berionni

Résultats de recherche: Contribution à un journal/une revueArticle

Résumé

The structures of the covalent Lewis adducts and/or frustrated Lewis pairs derived from 2- and 2,6-substituted pyridines with diaryl (Ar 2 CH +) and with the more bulky triaryl (Ar 3 C +) carbenium ions were analyzed by UV-vis and NMR spectroscopy. Thermodynamics (equilibrium constants) and kinetics (rate constants) of the associations of the carbon-centered Lewis acids Ar 2 CH + with a series of sterically hindered pyridines were investigated and used for the determination of the Lewis basicities and nucleophilicities, on the basis of the Mayr electrophilicity/nucleophilicity and Lewis acidity/basicity linear free energy relationships. In addition, methyl and benzhydryl cation affinities were computed to elucidate the respective steric and electronic contributions of the substituents to the nitrogen atom Lewis basicity. The influence of the size of the reference carbenium ion on the magnitude of the repulsion induced by the pyridine substituents (Me, t Bu in 2- or 2,6-positions) was also analyzed. Cumulated steric repulsion was found to decrease the reactivity of the nitrogen atom by up to 10 orders of magnitude.

langueAnglais
Pages3495-3504
Nombre de pages10
journalSynthesis (Germany)
Volume49
Numéro15
Les DOIs
étatPublié - 1 août 2017
Modification externeOui

Empreinte digitale

Pyridines
Alkalinity
Pyridine
Nitrogen
Ions
Lewis Acids
Atoms
Equilibrium constants
Ultraviolet spectroscopy
Acidity
Nuclear magnetic resonance spectroscopy
Free energy
Cations
Rate constants
Carbon
Positive ions
Thermodynamics
Kinetics
Acids

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    Follet, Elsa ; Zipse, Hendrik ; Lakhdar, Sami ; Ofial, Armin R. ; Berionni, Guillaume. / Nucleophilicities and Lewis Basicities of Sterically Hindered Pyridines. Dans: Synthesis (Germany). 2017 ; Vol 49, Numéro 15. p. 3495-3504
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    abstract = "The structures of the covalent Lewis adducts and/or frustrated Lewis pairs derived from 2- and 2,6-substituted pyridines with diaryl (Ar 2 CH +) and with the more bulky triaryl (Ar 3 C +) carbenium ions were analyzed by UV-vis and NMR spectroscopy. Thermodynamics (equilibrium constants) and kinetics (rate constants) of the associations of the carbon-centered Lewis acids Ar 2 CH + with a series of sterically hindered pyridines were investigated and used for the determination of the Lewis basicities and nucleophilicities, on the basis of the Mayr electrophilicity/nucleophilicity and Lewis acidity/basicity linear free energy relationships. In addition, methyl and benzhydryl cation affinities were computed to elucidate the respective steric and electronic contributions of the substituents to the nitrogen atom Lewis basicity. The influence of the size of the reference carbenium ion on the magnitude of the repulsion induced by the pyridine substituents (Me, t Bu in 2- or 2,6-positions) was also analyzed. Cumulated steric repulsion was found to decrease the reactivity of the nitrogen atom by up to 10 orders of magnitude.",
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    Follet, E, Zipse, H, Lakhdar, S, Ofial, AR & Berionni, G 2017, 'Nucleophilicities and Lewis Basicities of Sterically Hindered Pyridines' Synthesis (Germany), VOL. 49, Numéro 15, p. 3495-3504. DOI: 10.1055/s-0036-1590504

    Nucleophilicities and Lewis Basicities of Sterically Hindered Pyridines. / Follet, Elsa; Zipse, Hendrik; Lakhdar, Sami; Ofial, Armin R.; Berionni, Guillaume.

    Dans: Synthesis (Germany), Vol 49, Numéro 15, 01.08.2017, p. 3495-3504.

    Résultats de recherche: Contribution à un journal/une revueArticle

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    N2 - The structures of the covalent Lewis adducts and/or frustrated Lewis pairs derived from 2- and 2,6-substituted pyridines with diaryl (Ar 2 CH +) and with the more bulky triaryl (Ar 3 C +) carbenium ions were analyzed by UV-vis and NMR spectroscopy. Thermodynamics (equilibrium constants) and kinetics (rate constants) of the associations of the carbon-centered Lewis acids Ar 2 CH + with a series of sterically hindered pyridines were investigated and used for the determination of the Lewis basicities and nucleophilicities, on the basis of the Mayr electrophilicity/nucleophilicity and Lewis acidity/basicity linear free energy relationships. In addition, methyl and benzhydryl cation affinities were computed to elucidate the respective steric and electronic contributions of the substituents to the nitrogen atom Lewis basicity. The influence of the size of the reference carbenium ion on the magnitude of the repulsion induced by the pyridine substituents (Me, t Bu in 2- or 2,6-positions) was also analyzed. Cumulated steric repulsion was found to decrease the reactivity of the nitrogen atom by up to 10 orders of magnitude.

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    Follet E, Zipse H, Lakhdar S, Ofial AR, Berionni G. Nucleophilicities and Lewis Basicities of Sterically Hindered Pyridines. Synthesis (Germany). 2017 août 1;49(15):3495-3504. Disponible �, DOI: 10.1055/s-0036-1590504