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Reacciones de acoplamiento de alquinos catalizadas por níquel y dirigidas por alceno
Karen M Miller1, Torsak Luanphaisarnnont, Carmela Molinaro
1Massachusetts Institute of Technology, Department of Chemistry, Cambridge, Massachusetts, USA.
Journal of the American Chemical Society
|April 1, 2004
Resumen
Las reacciones de acoplamiento catalizadas por níquel de 1,3-eninas con aldehídos y epoxidos muestran una mayor reactividad y regioselectividad debido al alqueno conjugado. Esto permite la síntesis de valiosos productos de dieno y alcoholes alelicos.
Área de la Ciencia:
- Química orgánica es la química orgánica.
- Química organometálica Química orgánica de los metales.
- La catálisis es la catálisis.
Sus antecedentes:
- Las reacciones de acoplamiento catalizadas por níquel son cruciales en la síntesis orgánica.
- Las 1,3-eninas son bloques de construcción versátiles, pero su reactividad y regioselectividad en reacciones de acoplamiento pueden ser un desafío.
- El control de la regioselectividad en las transformaciones catalizadas por metales es un área clave de investigación.
Objetivo del estudio:
- Investigar el papel del alqueno conjugado en las reacciones de acoplamiento catalizadas por níquel de 1,3-eninas con aldehídos y epoxidos.
- Comprender el mecanismo que rige la reactividad y la regioselectividad.
- Desarrollar un método para la síntesis de 1,3-dienos altamente sustituidos y, posteriormente, de álcoholes alelo/homoalelo.
Principales métodos:
- Acoplamiento catalizado por níquel de 1,3-eninas con aldehídos y epoxidos.
- Variación sistemática de los sustituyentes de alquinos y grados de sustitución de alquenos.
- Estudios mecanicistas para investigar el papel del alqueno en la determinación de la regioselectividad.
- Subsecuente hidrogenación catalizada por el rodio de los productos de dieno.
Principales resultados:
- El alqueno conjugado en 1,3-eninos dirige uniformemente la regioselectividad en las reacciones de acoplamiento catalizadas por níquel.
- La reactividad se mejora significativamente, independientemente del sustituto de alquino o la sustitución de alqueno.
- Los productos de 1,3-dieno altamente sustituidos se sintetizan de manera eficiente.
- Una subsiguiente hidrogenación catalizada por el rodio proporciona acceso a alcoholes aleloides y homoaliloides previamente inaccesibles con alta regioselectividad.
Conclusiones:
- El alqueno conjugado juega un papel crítico en la dirección de la regioselectividad a través de la interacción temporal con el catalizador de níquel.
- Esta catálisis de níquel dirigida por alqueno ofrece un método poderoso y general para sintetizar dienes complejos.
- La metodología desarrollada proporciona una ruta novedosa a los alcoholes alilicos y homoalilicos sintetizados regioselectivamente.
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