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Quiral litio ((I) sales de binaftolato para la reacción enantioselectiva directa de tipo Mannich con un cambio de
Manabu Hatano1, Takahiro Horibe, Kazuaki Ishihara
1Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa, Nagoya 464-8603, Japan.
Journal of the American Chemical Society
|December 17, 2009
Resumen
Un nuevo sistema catalítico que utiliza sales de litio ((I) BINOLATO permite reacciones directas de tipo Mannich altamente estereoselectivas. Este método eficiente proporciona valiosos antiproductos a partir de compuestos 1,3-dicarbonilo bajo condiciones suaves.
Área de la Ciencia:
- Química orgánica es la química orgánica.
- La catálisis es la catálisis.
- Síntesis asimétrica de síntesis.
Sus antecedentes:
- La reacción de tipo Mannich es una reacción crucial de formación de enlaces carbono-carbono en la síntesis orgánica.
- Lograr una alta estereoselectividad, particularmente en las reacciones directas de Mannich con compuestos 1,3-dicarbonilo, sigue siendo un desafío.
- Los catalizadores existentes a menudo producen mezclas de productos sin / anti o carecen de estereoquímica definida.
Objetivo del estudio:
- Desarrollar una reacción de tipo Mannich directa altamente diastereoselectiva y enantioselectiva.
- Para utilizar las sales de litio ((I) BINOLATO como catalizadores duales ácido de Lewis y base de Brønsted.
- Para ampliar el alcance de los compuestos 1,3-dicarbonilo aplicables en las reacciones asimétricas de Mannich.
Principales métodos:
- Desarrollo del litio (I) sales de BINOLATO como catalizadores.
- Reacción de las aldiminas con varios compuestos 1,3-dicarbonilo (diketonas, cetoésteres, cetotioésteres, cetoamidas, cetolactonas).
- Optimización de las condiciones de reacción, incluyendo baja temperatura (-78 °C) y tiempos de reacción cortos (1-2 h).
Principales resultados:
- Alta actividad catalítica y selectividad lograda con sales de Li ((I) BINOLATO.
- Se observó una frecuencia de rotación excepcional (284 h-1), superando a los catalizadores anteriores.
- Formación selectiva de antiproductos a partir de cetóesteres acíclicos sin epimización en el centro de carbono alfa-terciario.
Conclusiones:
- Las sales de litio ((I) BINOLATO son catalizadores muy eficaces para las reacciones directas de tipo Mannich.
- El método desarrollado ofrece una ruta superior a los productos definidos estereoquímicamente.
- Este avance proporciona una herramienta valiosa para la síntesis asimétrica de moléculas orgánicas complejas.
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