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Updated: Mar 6, 2026
Facile Preparation of 2Z,4E-Dienamides by the Olefination of Electron-deficient Alkenes with Allyl Acetate
Published on: June 21, 2017
Phosphazene Catalyzed Addition to Electron-Deficient Alkynes: The Importance of Nonlinear Allenyl Intermediates upon
1Facultad de Ciencias Químicas, Universidad de Salamanca , Plaza de los Caídos 1-5, Salamanca E37004, Spain.
Abstract:
An ONIOM(QM/MM) study on the mechanism of the Michael addition to triple bonds catalyzed by chiral diiminophosphorane catalysts has been performed to understand the stereoselectivity of the product olefin. Our results are consistent with the experimental enantioselectivity, but more importantly, reveal that the Z vs E preference depends on the influence of the catalyst upon the geometry of the allenyl enolate formed in the addition step. These intermediates show an innate preference for a (Z)-configuration, although this can be suppressed by steric interactions due to a catalyst. This leads to two distinct mechanisms in which the kinetic basis for (E) or (Z)-stereoselectivity is determined by a different step. Bifunctional iminophosphorane catalysts are found to use steric interactions to override innate stereoelectronic effects of the allenyl enolate reactive intermediate.
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