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Probar el origen de la selectividad de la metátesis degenerada a través de la caracterización y la dinámica de los

Benjamin K Keitz¹, Robert H Grubbs

¹Arnold and Mabel Beckman Laboratories of Chemical Synthesis, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States.

Journal of the American Chemical Society

|September 17, 2011

Resumen

Los nuevos catalizadores de rutenio con carbenos N-heterocíclicos (NHC) muestran una preferencia por la metátesis degenerada. El ligando NHC influye en la tasa de intercambio de metileno, lo que afecta la selectividad del catalizador en las reacciones de metástasis.

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 herramienta poderosa en la síntesis orgánica.
Los catalizadores de rutenio son ampliamente utilizados para las reacciones de metatesis.
Comprender la selectividad del catalizador es crucial para optimizar los resultados sintéticos.

Objetivo del estudio:

Para preparar y caracterizar nuevos catalizadores de metatesis de fosfonio alquilideno rutenio con carbenos N-heterocíclicos (NHC).
Investigar el papel de los NHC en la influencia de la selectividad del catalizador, particularmente la preferencia por la metástasis degenerada.
Para dilucidar las vías mecanicistas que rigen el comportamiento de estos catalizadores en las reacciones de etileno y metástasis de cierre de anillo (RCM).

Principales métodos:

Síntesis de nuevos catalizadores de NHC de alquilideno de fosfonio y rutenio.
Caracterización de los rutenaciclobutanos intermedios mediante espectroscopia de RMN criogénica.
Estudios cinéticos de las reacciones de catalizadores con sustratos de etileno y RCM.

Principales resultados:

Los catalizadores se prepararon con éxito y mostraron una preferencia por la metástasis degenerada.
Los rutenaciclobutanos formados a partir de etileno mostraron tasas de cambio variables de metileno, lo que pone de relieve el papel del NHC.
Se observó la formación de un nuevo rutenaciclo sustituido por β-alquilo.
Los rutenaciclos relevantes para la MCR mostraron mayores barreras cinéticas para la disociación del producto en comparación con los catalizadores existentes.

Conclusiones:

Los carbenos N-heterocíclicos influyen significativamente en la selectividad degenerada/productiva de los catalizadores de metástasis de rutenio.
Las diferencias cinéticas observadas proporcionan información sobre los factores que rigen el rendimiento del catalizador en RCM.
Estos hallazgos contribuyen al diseño racional de catalizadores de metatesis más selectivos y eficientes.

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