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La alilación asimétrica Sakurai-Hosomi catalizada por plata de las cetonas
Manabu Wadamoto1, Hisashi Yamamoto
1Department of Chemistry, The University of Chicago, Illinois 60637, USA.
Journal of the American Chemical Society
|October 20, 2005
Resumen
Un nuevo sistema catalizador de fluoruro de plata (AgF) y (R) -DIFLUORPHOS cataliza de manera eficiente la alilación asimétrica Sakurai-Hosomi de las cetonas. Este método logra una alta enantioselectividad para los alcoholes homoalílicos terciarios y permite la crotilación enantioselectiva.
Área de la Ciencia:
- Química orgánica es la química orgánica.
- La catálisis es la catálisis.
- Síntesis asimétrica de síntesis.
Sus antecedentes:
- La alilación Sakurai-Hosomi es una reacción crucial para la formación de enlaces carbono-carbono.
- El desarrollo de catalizadores eficientes y enantioselectivos para esta reacción sigue siendo un área activa de investigación.
- Los métodos anteriores a menudo requieren sustratos específicos o condiciones duras.
Objetivo del estudio:
- Desarrollar un sistema catalítico altamente enantioselectivo para la alilación asimétrica Sakurai-Hosomi de cetonas simples.
- Para investigar la influencia de los disolventes y aditivos en el rendimiento del catalizador.
- Para explorar la aplicación de este sistema a varios sustratos cetónicos y reacciones de alilación.
Principales métodos:
- Formación de un complejo 1:1 entre el fluoruro de plata (AgF) y (R) -DIFLUORPHOS.
- Optimización de las condiciones de reacción, incluido el disolvente (THF) y el co-catalizador de metanol.
- Aplicación del catalizador AgF/(R) -DIFLUORPHOS a una gama de cetonas simples y cetonas conjugadas.
- Investigación de la crotilación regio-, diastereoselectiva y enantioselectiva con el uso de E- o Z-crotyltrimethoxysilane.
Principales resultados:
- El complejo AgF / R-DIFLUORPHOS demostró una alta actividad catalítica y enantioselectividad (hasta el 96% ee) para la alilación de cetonas simples.
- El tetrahidrofurano (THF) como disolvente mejoró significativamente la reactividad.
- La adición de metanol (1 equiv) mejoró la rotación del catalizador.
- El sistema produjo exclusivamente 1,2-adductos con cetonas conjugadas.
- Se logró con éxito la crotilación regioselectiva, diastereoselectiva y enantioselectiva, con proporciones similares de diastereómeros observadas para los E- y Z-alisilanos.
Conclusiones:
- El complejo AgF/(R) -DIFLUORPHOS 1:1 es un catalizador muy eficaz para la alilación asimétrica Sakurai-Hosomi.
- Este sistema catalítico ofrece una amplia aplicabilidad a varias cetonas, produciendo alcoholes homoalílicos terciarios con excelente enantioselectividad.
- Los hallazgos destacan la utilidad de los alilsilanos racémicos en las reacciones de alilación enantioselectivas, ampliando el alcance de la síntesis asimétrica.
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