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Acoplamiento cruzado quimioselectivo entre dos enlaces C (arilo) -O diferentes y no activados habilitados por

Jinghua Tang¹, Liu Leo Liu², Shangru Yang¹

¹Key Laboratory of Green Chemistry & Technology, Ministry of Education, College of Chemistry, Sichuan University, Chengdu 610064, China.

Journal of the American Chemical Society

|April 18, 2020

Resumen

Este estudio introduce la catálisis de cromo para el acoplamiento cruzado de enlaces de éter de arilo y éster no activados. Este nuevo método une de manera eficiente dos enlaces distintos de C ((aryl) O en condiciones suaves utilizando un sistema de catalizador de bajo costo.

Área de la Ciencia:

Química orgánica
Química organometálica
Catálisis

Sus antecedentes:

La activación del enlace carbono-oxígeno (CO) es crucial en la síntesis orgánica.
Las reacciones de acoplamiento cruzado generalmente involucran grupos funcionales más reactivos, dejando sustratos desafiantes de enlaces C-O no activados.
El desarrollo de métodos catalíticos para la activación de enlaces robustos de carbono-arilo es altamente deseable para la eficiencia sintética.

Objetivo del estudio:

Indicar el primer ejemplo de acoplamiento entre dos enlaces C ((arilo) -O diferentes y no activados.
Desarrollar un sistema catalítico que utilice cromo para esta transformación.
Para lograr el acoplamiento selectivo de éteres metílicos de arilo y ésteres de arilo a través de la escisión del enlace C-O.

Principales métodos:

Utilizando una sal de cromo (CrCl2) de bajo costo como precursor del catalizador.
Utilizando el 4,4'-di-tert-butil-2,2'-dipiridil (dtbpy) como ligando.
Utilización de magnesio (Mg) como reductor para generar especies activas de cromo de baja valencia.
Investigando el mecanismo de reacción que implica la activación inicial del enlace C (arilo) -O, la reducción y la eliminación reductora.

Principales resultados:

Se ha demostrado el éxito del acoplamiento cruzado de dos enlaces arilo-C2 diferentes y no activados.
Se obtiene una alta reactividad utilizando un sistema Cr (II) /dtbpy/Mg en condiciones suaves.
Se demostró el acoplamiento selectivo de derivados de éter metílico de arilo con ésteres de arilo.
Se propuso un mecanismo que implica la activación inicial del enlace C (arilo) -O del éter fenilmetilo facilitado por dtbpy y un auxiliar de o-imina.

Conclusiones:

Este trabajo presenta un método pionero catalizado por cromo para el acoplamiento de enlaces C (arilo) -O no activados.
El sistema desarrollado ofrece una vía suave y eficiente para sintetizar compuestos biarílicos a partir de éteres y ésteres de arilo fácilmente disponibles.
Los hallazgos abren nuevas vías para utilizar enlaces robustos de C-O en la catálisis de acoplamiento cruzado.

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