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Aminación catalítica C-H mediada por imidos de cobalto de dipirrina

Yunjung Baek¹, Theodore A Betley¹

¹Department of Chemistry and Chemical Biology , Harvard University , 12 Oxford Street , Cambridge , Massachusetts 02138 , United States.

Journal of the American Chemical Society

|April 25, 2019

Resumen

Este estudio introduce un nuevo cobalto (I) sintón que facilita una catálisis de aminación C-H eficiente. Los complejos imido de cobalto, particularmente cuando se coordinan con piridina, demuestran una mayor reactividad y rotación catalítica para la funcionalización de enlaces C-H.

Área de la Ciencia:

Química organometálica
Catálisis
Química sintética

Sus antecedentes:

Desarrollo de nuevos complejos de metales de transición para aplicaciones catalíticas.
Exploración de los complejos de cobalto en las reacciones de funcionalización C-H.
Comprender la reactividad de las especies de cobalto imido.

Objetivo del estudio:

Para sintetizar y caracterizar un nuevo cobalto
Investigar la reactividad de los complejos imido de cobalto en la aminación C-H.
Elucidar el mecanismo de la aminación C-H catalizada por cobalto.

Principales métodos:

Reducción de un complejo de cobalto (II) a un sintón de cobalto (I) utilizando grafito de potasio.
Tratamiento del complejo de cobalto (I) con azidas alquilo para formar complejos de cobalto (III) imido.
Difracción de rayos X de un solo cristal para la confirmación estructural.
H experimentos de titulación de RMN para estudiar la coordinación de la piridina.
Estudios cinéticos, incluidos los experimentos de efecto de isótopos cinéticos, para sondear el mecanismo de reacción.

Principales resultados:

Síntesis exitosa de un nuevo cobalto (I) sintón, (Ar) Co (I).
Formación de complejos de imido de alquilo de cobalto (III) de tres coordenadas, (^ArL) Co (NR).
Observación de la aminación intramolecular de C-H que conduce a la formación de pirrolidina.
La coordinación de piridina con el complejo imido de cobalto aumenta la reactividad de la aminación C-H y el volumen de negocios catalítico.
Los estudios cinéticos sugieren una vía radical de dos pasos para la aminación C-H.

Conclusiones:

El nuevo cobalto (I) sintón es un precursor versátil para los complejos de cobalto (III) imido.
Los complejos de cobalto ligado a piridina (III) son catalizadores muy eficaces para la aminación C-H.
La mayor reactividad se atribuye a una mayor población de estado de espín y una disminución del campo cristalino en la coordinación de piridina.
El estudio proporciona información mecanicista sobre la aminación C-H catalizada por cobalto a través de una vía radical.

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