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Hidroacilación intermolecular: catalizadores de rodio de alta actividad que contienen ligandos de difosfina de ángulo

Adrian B Chaplin¹, Joel F Hooper, Andrew S Weller

¹Department of Chemistry, Inorganic Chemistry Laboratories, University of Oxford, South Parks Road, Oxford OX1 3QR, UK.

Journal of the American Chemical Society

|February 14, 2012

Resumen

Los catalizadores de rodio altamente eficientes permiten la hidroacilación intermolecular de alquenos y alquinas no activados utilizando aldehídos. Estos catalizadores funcionan a bajas cargas, logrando altas frecuencias de rotación para la síntesis orgánica valiosa.

Área de la Ciencia:

Química organometálica Química orgánica de los metales.
La catálisis de la catálisis.
Síntesis orgánica La síntesis orgánica.

Sus antecedentes:

Los complejos de rodio con ligandos de difosfina con puente de metileno son eficaces precatalizadores.
Estos catalizadores facilitan la hidroacilación intermolecular de alquenos y alquinas no activados.
La reacción utiliza aldehídos sustituidos por β-S como agentes aciladores.

Objetivo del estudio:

Desarrollar precatalizadores de rodio prácticos y altamente eficientes para la hidroacilación intermolecular.
Caracterizar los complejos de intermedios y productos involucrados en el ciclo catalítico.
Para aclarar el mecanismo catalítico, incluidos los pasos clave y las posibles reacciones secundarias.

Principales métodos:

Síntesis y caracterización de nuevos complejos rodio-difosfina.
Reacciones estequiométricas para aislar y estudiar el hidruro de acilo intermedio y los productos de descarbonización.
Cristalografía de rayos X para la determinación estructural de complejos clave.
Efectos de Isótopos Cinéticos (KIE) y estudios de etiquetado de deuterio para sondear los mecanismos de reacción.

Principales resultados:

Se prepararon complejos de rodio estables en banco con ligandos de difosfina con puente de metileno.
Estos complejos catalizan eficientemente la hidroacilación intermolecular de diversos alquenos y alquinas con aldehídos.
Se caracterizaron el hidruro de acilo intermedio y los productos de descarbonización, proporcionando conocimientos mecánicos.
Las condiciones optimizadas permitieron cargas de catalizador muy bajas (0.1 mol %) y altas frecuencias de rotación (>300 h−1).

Conclusiones:

La selección juiciosa del disolvente y la concentración permite ajustar entre la descarbonización y la hidroacilación productiva.
Un mecanismo propuesto involucra la adición oxidativa reversible y los pasos de inserción de alqueno.
El sistema catalítico demuestra una alta eficiencia y amplia aplicabilidad en la síntesis orgánica.

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