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Un sorprendente "interruptor" mecánico en la activación del ácido de Lewis: un enfoque bifuncional y asimétrico para
Ciby J Abraham1, Daniel H Paull, Tefsit Bekele
1Department of Chemistry, New Chemistry Building, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, USA.
Journal of the American Chemical Society
|December 5, 2008
Resumen
Los enolados metálicos quirales reaccionan con las o-quinonas a través de una reacción secuencial de hetero-Diels-Alder/apertura de anillo. Este nuevo método produce de manera eficiente derivados de carbonilo alfa-hidroxilados altamente enriquecidos con enantio.
Área de la Ciencia:
- Química orgánica es la química orgánica.
- Catalización asimétrica por catálisis asimétrica.
- Mecanismo de reacción Mecanismo de reacción
Sus antecedentes:
- Las reacciones Hetero-Diels-Alder son cruciales para la formación de compuestos cíclicos.
- Las o-quinonas son sustratos versátiles en la síntesis orgánica.
- Los enolados metálicos quirales ofrecen vías de reactividad únicas.
Objetivo del estudio:
- Para investigar una nueva bifuncional, secuencial hetero-Diels-Alder / anillo de apertura de la reacción.
- Desarrollar un método para sintetizar derivados de carbonilo alfa-hidroxilados enantioenriquecidos.
- Para dilucidar el mecanismo de reacción e identificar los componentes catalíticos clave.
Principales métodos:
- Detección de ácidos de Lewis y derivados de alcaloides de cinchona.
- Estudios sintéticos y mecanicistas detallados.
- Análisis espectroscópico (IR, UV, RMN) y modelado molecular.
Principales resultados:
- Los enolados quirales de ceteno con complejo metálico reaccionan con las o-quinonas con alto rendimiento y enantioselectividad.
- trans-(Ph(3)P)(2)PdCl(2) aumentó significativamente el rendimiento y la velocidad de la reacción.
- Se observó un interruptor mecanicista que favorecía el tándem de enolados metálicos activados con base de Lewis y ácido de Lewis.
Conclusiones:
- Se ha establecido una nueva vía sintética para los derivados de carbonilo alfa-hidroxilados.
- La reacción se produce a través de una vía mecánica única que involucra enolados metálicos.
- El método es aplicable a la síntesis de objetivos farmacéuticos con alta eficiencia.
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