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Interrogación mecanicista de las hidroarilaciones de alquinos catalizadas por complejos de cobalto de un solo

Benjamin A Suslick^1,2, T Don Tilley^1,2

¹Department of Chemistry, University of California, Berkeley, California 94720, United States.

Journal of the American Chemical Society

|May 28, 2020

Resumen

Este estudio identifica un nuevo complejo de cobalto ((-I) como el catalizador activo para la orto-hidroarilación de los alquinos. Las investigaciones mecanicistas revelan una vía concertada de metalización-deproprotonación y Z-selectividad.

Área de la Ciencia:

Química organometálica
Catálisis
Mecanismos de reacción

Sus antecedentes:

Los catalizadores de cobalto anteriores para la ortohidroarilación carecían de mecanismos definidos.
Las especies activas de cobalto permanecieron sin identificar, lo que obstaculizó el desarrollo posterior.

Objetivo del estudio:

Para aclarar el mecanismo de la orto-hidroarilación catalizada por cobalto.
Identificar las especies activas de cobalto y comprender las dependencias del sustrato.

Principales métodos:

Análisis mecanicista utilizando complejos de cobalto reducido aislables.
Reacciones estequiométricas con reactivos de Grignard y estudios cinéticos.
Mediciones del efecto isotópico primario.

Principales resultados:

Se identificó un complejo de un solo componente de cobalto ((-I) como el precatalizador activo.
La iniciación del catalizador incluye la eliminación/desprotonación de beta-H.
Se propuso un mecanismo concertado de metalización-deprotonación (CMD) para la activación del enlace C-H.
La coordinación alquina influye en la cinética y la selectividad de la reacción.
La isomerización de la olefina fuera del ciclo por las especies de cobalto dictan la selectividad Z.

Conclusiones:

El complejo de cobalto ((-I) es un catalizador altamente reactivo para la ortohidroarilación.
La reacción se produce a través de un mecanismo de CMD con una división C-H que determina la velocidad.
La comprensión de estos mecanismos permite el diseño racional de catalizadores para la funcionalización de alquinos.

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