Trans‐Concerted Addition to Alkynes: the case of Ynamide Silylzincation - Réactivité organométallique et catalyse pour la synthèse
Article Dans Une Revue Chemistry - A European Journal Année : 2024

Trans‐Concerted Addition to Alkynes: the case of Ynamide Silylzincation

Résumé

An original concerted antarafacial mechanism for the addition of diorganosilyl‐zinc reagents across the C–C triple bond in ynamides is computationally investigated using DFT calculations. This concerted mechanism, leading to a trans‐product in only one step, results in the formation of a Si–C and a Zn–C σ‐bonds on opposite sides of the π‐system. We demonstrate that the mechanism going through a η2‐vinyl intermediate and the proposal of a radical chain pathway are energetically unsustainable. The retained concerted antarafacial pathway is tested on experimental selectivities: the regioselectivity, in favor of the silyl β‐addition in ynamide, and stereoselectivity, which is cis‐ with (Me2PhSi)2Zn but trans‐ with [(Me3Si)3Si]2Zn, are well reproduced by DFT calculations. The regio‐ and stereoselectivity are discussed using the activation strain model and a chemical bonding analysis.

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Chimie
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hal-04595675 , version 1 (16-10-2024)

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Frédéric Guégan, Fabrice Chemla, Franck Ferreira, Hélène Gérard, Alejandro Perez-Luna, et al.. Trans‐Concerted Addition to Alkynes: the case of Ynamide Silylzincation. Chemistry - A European Journal, 2024, 30 (43), ⟨10.1002/chem.202401751⟩. ⟨hal-04595675⟩
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