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Alquenilación Ni-Catalizada de enolados cetónicos bajo condiciones leves: Identificación y optimización del
Michael Grigalunas1, Tobias Ankner2, Per-Ola Norrby1,3
1†Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States.
Journal of the American Chemical Society
|May 30, 2015
Resumen
Una nueva reacción de acoplamiento cruzado catalizada por níquel une eficientemente los enolados cetónicos con los haluros de alquenilo. Este método proporciona altos rendimientos para la síntesis de moléculas orgánicas complejas.
Área de la Ciencia:
- Química orgánica es la química orgánica.
- La catálisis es la catálisis.
- Metodología sintética de la metodología sintética.
Sus antecedentes:
- Las reacciones de acoplamiento cruzado son fundamentales en la síntesis orgánica.
- El desarrollo de sistemas catalíticos eficientes para la formación de enlaces C-C es crucial.
- Los enolados cetónicos son nucleófilos versátiles, pero su acoplamiento cruzado puede ser un desafío.
Objetivo del estudio:
- Desarrollar un nuevo procedimiento catalizado por níquel para el acoplamiento cruzado de enolados cetónicos con halogenuros de alquenilo.
- Para optimizar las condiciones de reacción para obtener altos rendimientos y un amplio alcance de sustrato.
- Para identificar las especies catalíticas activas y descartar la contaminación por paladio.
Principales métodos:
- Se utilizó níquel ((0) bis ((1,5-ciclooctadieno) (Ni ((cod) 2) como el precatalizador.
- Se emplean ligandos de carbenos N-heterocíclicos (NHC) para estabilizar el catalizador de níquel.
- Investigó el papel del yoduro de litio (LiI) como aditivo.
- Se examinaron varios enolados de litio de cetonas aromáticas y alifáticas y halogenuros de alquenilo.
- Temperatura y tiempo de reacción optimizados para un acoplamiento eficiente.
Principales resultados:
- Se logró el acoplamiento intermolecular de enolados de litio de cetonas aromáticas y alifáticas con diversos halogenuros de alquenilo.
- Se obtienen rendimientos de hasta el 90% en condiciones óptimas.
- Identificó Ni ((cod) 2) en combinación con un ligando NHC y LiI como el sistema catalítico efectivo.
- Demostró que el paladio es incompetente como catalizador en las condiciones optimizadas basadas en níquel, a pesar de los resultados engañosos iniciales debido a la contaminación de rastro de paladio en un ligando comercial.
Conclusiones:
- Desarrolló con éxito un robusto acoplamiento cruzado catalizado por Ni de enolados cetónicos con haluros de alquenilo.
- El protocolo optimizado ofrece un método de alto rendimiento y eficiente para la formación de enlaces C-C.
- El estudio aclara el sistema catalítico activo, distinguiéndolo de las posibles vías catalizadas por el paladio.
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