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La reacción de acoplamiento cruzado catalizada por el paladio de los anhídridos carboxílicos con ácidos
Lukas J Goossen1, Debasis Koley, Holger L Hermann
1Max-Planck-Institut für Kohlenforschung, D-45470 Mülheim an der Ruhr, Germany. goossen@chemie.uni-kl.de
Journal of the American Chemical Society
|August 4, 2005
Resumen
Este estudio utilizó cálculos DFT para modelar la reacción de Suzuki. Los complejos aniónicos de paladio muestran una mayor actividad catalítica debido a una mejor coordinación electrofílica del carbono, no a los intermediarios de cinco coordenadas.
Área de la Ciencia:
- Química organometálica Química orgánica de los metales.
- Química computacional es la química computacional.
- La catálisis es la catálisis.
Sus antecedentes:
- La reacción de Suzuki es un método de acoplamiento cruzado ampliamente utilizado.
- La comprensión de los mecanismos de reacción es crucial para optimizar los procesos catalíticos.
- Las transformaciones catalizadas por el paladio son vitales en la síntesis orgánica.
Objetivo del estudio:
- Para dilucidar el mecanismo catalítico de la reacción de Suzuki usando ácido fenilborónico y anhídrido acético como un sistema modelo.
- Investigar el papel de los complejos de paladio neutro versus aniónico en el ciclo catalítico.
- Explorar la influencia de las estructuras intermedias en la actividad catalítica.
Principales métodos:
- Se emplearon cálculos de la Teoría Funcional de Densidad (DFT).
- Se utilizó el nivel de teoría BP86/6-31G.
- Se analizaron dos ciclos catalíticos distintos, uno neutro y otro aniónico.
Principales resultados:
- Los perfiles de reacción calculados se alinean bien con las observaciones experimentales, lo que indica energías de activación moderadas para ambas vías.
- Ambos ciclos catalíticos involucran predominantemente paladio cuadrado plano de configuración cis (II) difosfina intermedios.
- No se encontró evidencia de intermediarios de paladio ((II) de cinco coordenadas en este sistema de modelos.
- Los complejos aniónicos exhiben una mayor actividad catalítica, atribuida a una coordinación superior a los electrófilos de carbono.
Conclusiones:
- El estudio proporciona información mecanicista detallada sobre el modelo de reacción de Suzuki.
- Los complejos de paladio aniónico pueden mejorar la catálisis a través de una unión electrofílica más fuerte en lugar de a través de intermediarios de cinco coordenadas.
- El paso de transmisión implica la disociación del ligando de fosfina y una base de acetato puente en el estado de transición.
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