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Complejos de cobre de ligandos de nitrógeno aniónico en la amidación e imidación de haluros de arilo

Jesse W Tye¹, Zhiqiang Weng, Adam M Johns

¹Departments of Chemistry, University of Illinois, Urbana, Illinois 61801, USA.

Journal of the American Chemical Society

|July 4, 2008

Resumen

Los complejos de cobre (I) imidato y amidato son intermediarios clave en las reacciones de acoplamiento C-N catalizadas por cobre. Estos complejos facilitan la amidación del haluro de arilo, con estudios mecanicistas que apoyan una vía directa de escisión de enlaces carbono-halógeno.

Área de la Ciencia:

Química organometálica Química orgánica de los metales.
La catálisis de la catálisis.
Química sintética de la química sintética.

Sus antecedentes:

La amidación catalizada por cobre de haluros de arilo es una transformación crucial en la síntesis orgánica.
La naturaleza precisa de los intermediarios de cobre en estas reacciones sigue siendo objeto de investigación.
Se sabe que los ligandos N,N-donantes quelantes estabilizan los complejos de cobre.

Objetivo del estudio:

Para sintetizar y caracterizar el cobre (I) imidato y los complejos de amidato.
Investigar el papel de estos complejos como intermediarios en las reacciones de acoplamiento C-N catalizadas por cobre.
Para dilucidar el mecanismo de la amidación catalizada por el cobre de haluros de arilo.

Principales métodos:

Síntesis y caracterización de complejos de cobre utilizando difracción de rayos X.
Estudios de la fase de solución que incluyen mediciones de conductividad y espectroscopia de RMN.
Reacciones estequiométricas y catalíticas con varios haluros de arilo (iodoarenos, bromoarenos, cloroarenos).

Principales resultados:

Se sintetizaron complejos de cobre (I) imidato y amidato, que existen en formas neutras o iónicas dependiendo del ligando y el disolvente.
Estos complejos catalizaban efectivamente el acoplamiento de C-N con iodoarenos y bromoarenos, pero mostraban una reactividad reducida con los cloroarenos.
Los estudios mecánicos, incluidas las reacciones con sustratos específicos y el análisis computacional, argumentan en contra de las vías de cobre radical o aniónico.

Conclusiones:

Los complejos aislados de cobre ((I) imidato y amidato son de hecho intermedios en la amidación de haluro de arilo catalizado por cobre.
El mecanismo de reacción probablemente implica la escisión directa del enlace carbono-halógeno dentro de la esfera de coordinación de cobre.
Los hallazgos proporcionan información crítica sobre el ciclo catalítico de la formación de enlaces C-N mediados por cobre.

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