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La acilación asimétrica catalizada por metallofosfito de las amidas alfa, beta insaturadas catalizadas por
Mary R Nahm1, Justin R Potnick, Peter S White
1Department of Chemistry, University of North Carolina at Chapel Hill, 27599-3290, USA.
Journal of the American Chemical Society
|February 24, 2006
Resumen
Un nuevo catalizador de fosfito TADDOL permite adiciones conjugadas altamente enantioselectivas de silanos de acilo a amidas insaturadas. Los productos resultantes se pueden enriquecer fácilmente hasta un alto exceso enantiomérico, produciendo valiosos intermedios para una síntesis posterior.
Área de la Ciencia:
- Química orgánica es la química orgánica.
- La catálisis de la catálisis.
- Síntesis asimétrica de síntesis.
Sus antecedentes:
- Las reacciones de adición conjugada son fundamentales en la síntesis orgánica.
- La catálisis enantioselectiva es crucial para producir moléculas quirales.
- Los silanos de acilo son reactivos versátiles en la formación de enlaces carbono-carbono.
Objetivo del estudio:
- Desarrollar un sistema catalítico altamente enantioselectivo para la adición conjugada de silanos de acilo.
- Explorar el alcance y la utilidad del sistema catalítico desarrollado.
- Para aclarar los aspectos clave del mecanismo de reacción.
Principales métodos:
- El uso de un fosfito TADDOL derivado de l-mentona (6b) como catalizador quiral.
- Adición conjugada enantioselectiva de p-metoxibenzoil ciclohexilidimetilsilano a los derivados de N,N-dimetil acrilamida.
- Enriquecimiento de productos a través de la recristalización.
- Desilación y oxidación de Baeyer-Villiger para otras transformaciones.
- Difracción de rayos X y experimentos cruzados para estudios mecanicistas.
Principales resultados:
- El fosfito 6b de TADDOL catalizó adiciones conjugadas altamente enantioselectivas (hasta el 99% ee).
- Los productos fueron sometidos a fácil enantioenriquecimiento tras la recristalización.
- La desilación proporcionó productos formales de adición de Stetter, y la subsiguiente oxidación produjo productos de éster.
- La difracción de rayos X reveló influencias estructurales en la catálisis.
- Los experimentos de cruce confirmaron la naturaleza intramolecular de la migración del silicio.
Conclusiones:
- El catalizador de fosfito TADDOL desarrollado es eficaz para las adiciones de conjugados enantioselectivos de silanos de acilo.
- La reacción proporciona acceso a valiosos intermediarios quirales a través de transformaciones posteriores.
- El estudio proporciona conocimientos mecanicistas sobre el ciclo catalítico, incluida la migración intramolecular de silicio.
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