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A Two-Step Protocol for Umpolung Functionalization of Ketones Via Enolonium Species
Published on: August 16, 2018
Alilación conjugada asimétrica Ni-catalizada de las enonas activadas
Joshua D Sieber1, James P Morken
1Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, Massachusetts 02467, USA.
Journal of the American Chemical Society
|March 15, 2008
Resumen
Este estudio detalla una reacción catalizada por níquel para la alilación enantioselectiva de cetonas de dialquilideno utilizando el éster de pinacol del ácido allibórnico. Se lograron altas enantioselectividades, favoreciendo el sitio de benzilideno en sustratos complejos.
Área de la Ciencia:
- Química organometálica Química orgánica de los metales.
- Catalización asimétrica por catálisis asimétrica.
- Química orgánica sintética y orgánica.
Sus antecedentes:
- Las cetonas de dialquilideno son versátiles intermediarios sintéticos.
- La alilación enantioselectiva es crucial para la síntesis de moléculas quirales.
- Desarrollar sistemas catalíticos eficientes para estas transformaciones sigue siendo un desafío.
Objetivo del estudio:
- Desarrollar una nueva adición enantioselectiva catalizada por níquel del éster pinacol del ácido alilborónico (allylB(pin)) a las cetonas de dialquilideno.
- Para investigar el mecanismo de la reacción y el alcance del sustrato.
- Para lograr altas enantioselectividades en el proceso de alilación.
Principales métodos:
- Reacción catalizada por níquel empleando el éster de pinacol del ácido alilborónico.
- Uso de cetonas de dialquilideno no simétricas como sustratos.
- El ligando quiral 14 se utilizó para inducir la enantioselectividad.
Principales resultados:
- La reacción demostró una alta eficacia con varias cetonas de dialquilideno.
- Se observó una preferencia por la alilación en el sitio del benzilideno en sustratos no simétricos.
- Se obtuvieron enantioselectividades que oscilaban entre el 91 y el 94% ee con el ligando quiral 14.
- El mecanismo propuesto implica la formación de un complejo pi-alilo insaturado seguido de una eliminación reductora.
Conclusiones:
- Se ha establecido una alilación enantioselectiva catalizada por níquel altamente efectiva de las cetonas de dialquilideno.
- El método proporciona acceso a productos quirales con excelente enantiocontrol.
- El mecanismo de reacción ofrece información sobre los ciclos catalíticos mediados por níquel.
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