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Heterogeneous Removal of Water-Soluble Ruthenium Olefin Metathesis Catalyst from Aqueous Media Via Host-Guest Interaction
Published on: August 23, 2018
Z-Selectividad en la metátesis de olefinas con catalizadores Ru quelados: estudios computacionales del mecanismo y la
Peng Liu1, Xiufang Xu, Xiaofei Dong
1Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, USA.
Journal of the American Chemical Society
|January 11, 2012
Resumen
Los catalizadores de rutenio quelado promueven la metátesis Z-selectiva de la olefina dirigiendo el acercamiento de la olefina hacia el lado, a diferencia de los catalizadores no quelados. Las interacciones estéricas con el ligando de carbenos N-heterocíclicos favorecen la formación de isómeros Z.
Área de la Ciencia:
- Química organometálica Química orgánica de los metales.
- La catálisis es la catálisis.
- Síntesis orgánica La síntesis orgánica.
Sus antecedentes:
- La metátesis de olefinas es una reacción vital en la síntesis orgánica.
- Lograr una alta estereoselectividad, particularmente la Z-selectividad, sigue siendo un desafío.
- Los catalizadores de rutenio (Ru) son ampliamente utilizados, pero sus mecanismos de selectividad requieren una mayor aclaración.
Objetivo del estudio:
- Para investigar los orígenes de la Z-selectividad en las reacciones de metátesis de olefinas catalizadas por complejos de rutenio quelados.
- Para dilucidar la vía mecanicista que rige el resultado estereoquímico.
- Comprender el papel del ligando del carbeno N-heterocíclico (NHC) en la dirección de la selectividad.
Principales métodos:
- Los cálculos de la teoría funcional de la densidad (DFT) se emplearon para modelar el ciclo catalítico.
- El análisis computacional se centró en la trayectoria de aproximación de la olefina y los estados de transición.
- Se analizaron las interacciones estéricas entre el sustrato y el catalizador.
Principales resultados:
- Los catalizadores de Ru quelados favorecen un acercamiento de la olefina desde la posición "lateral", distinta de la vía "confinada hacia abajo" de los catalizadores no quelados.
- Se identificaron repulsiones estéricas significativas entre los sustituyentes de olefinas y el N-sustituto del ligando NHC.
- Se descubrió que estos factores estéricos eran los principales impulsores de la alta selectividad Z observada.
Conclusiones:
- La única vía de aproximación "lateral" en los catalizadores Ru quelados es responsable de la selectividad Z.
- El diseño del ligando de carbenos N-heterocíclicos, específicamente el N-sustituto, es crucial para controlar la estereoquímica.
- Este estudio proporciona una comprensión mecanicista para el diseño de catalizadores de metátesis de olefinas más selectivos.
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