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El control cinético y termodinámico de la activación de C ((sp2) -H permite la borilación selectiva del sitio
Jose B Roque1, Alex M Shimozono1, Tyler P Pabst1
1Department of Chemistry, Princeton University, Princeton, NJ 08544, USA.
Science (New York, N.Y.)
|December 7, 2023
Resumen
Los nuevos catalizadores de cobalto con ligandos de piridina dicarbeno (ACNC) sustituidos por N-alquilo-imidazol permiten la borilación selectiva de C-H de diversos arenos. Este avance permite la funcionalidad remota sin dirigir grupos, avanzando la catálisis de metales de transición.
Área de la Ciencia:
- Química organometálica
- Catálisis
- Química sintética
Sus antecedentes:
- El diseño de catalizadores para la funcionalización selectiva de enlaces carbono-hidrógeno (C-H) sin grupos de dirección o control estérico es un desafío significativo.
- Los catalizadores de metales de transición de primera fila a menudo tienen problemas con el amplio alcance del sustrato y la selectividad del sitio.
Objetivo del estudio:
- Desarrollar nuevos precatalizadores de cobalto para la borilación no dirigida de C-H.
- Ampliar el alcance de la funcionalización C-H para incluir sustratos difíciles como los fluoroaromáticos y las arenas ricas en electrones.
- Investigar la base mecanicista de la selectividad del sitio en la borilación C-H catalizada por cobalto.
Principales métodos:
- Síntesis de precatalizadores de cobalto con ligandos de pinzas de piridina dicarbeno (ACNC) sustituidos por N-alquilo-imidazol.
- Aplicación de los catalizadores a la borilación de varios compuestos aromáticos y heteroaromáticos.
- Estudios mecánicos que incluyen análisis cinéticos y termodinámicos de las vías de activación de C-H.
- Exploración de la selectividad del sitio conmutable utilizando diferentes reactivos de boro.
Principales resultados:
- Los precatalizadores de cobalto soportados por ACNC permitieron la borilación no dirigida y remota de fluoroaromáticos.
- El alcance del catalizador se amplió a arenas ricas en electrones, piridinas y arenas metoxiladas.
- Los estudios mecánicos revelaron una preferencia cinética para la activación de meta-CH, en contraste con las preferencias termodinámicas.
- Demostración preliminar de la selectividad del sitio conmutable mediante la variación del reactivo de boro.
Conclusiones:
- Los precatalizadores de cobalto con ligandos ACNC ofrecen una poderosa plataforma para la berilación selectiva de C-H.
- Los catalizadores desarrollados superan las limitaciones en el alcance del sustrato y la dependencia del grupo de dirección para la funcionalización C-H.
- Comprender el control cinético frente al termodinámico proporciona información para el diseño de futuros catalizadores selectivos.
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