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Control electrostático de la regioselectividad en la hidroarilación catalizada por Au
Vivian M Lau1, William C Pfalzgraff1, Thomas E Markland1
1Department of Chemistry, Stanford University , 337 Campus Drive, Stanford, California 94305, United States.
Journal of the American Chemical Society
|February 23, 2017
Resumen
El control de las reacciones catalíticas con el emparejamiento iónico dirige selectivamente la formación de productos. Las interacciones electrostáticas entre los conteriones y los catalizadores ajustan los estados de transición, mejorando la regioselectividad hasta 12 veces.
Área de la Ciencia:
- Catálisis
- Química orgánica
- Química computacional
Sus antecedentes:
- Las vías de reacción en competencia a menudo presentan estados de transición con distribuciones de carga distintas.
- Aprovechar estas diferencias de carga para controlar la selectividad de la reacción es un desafío.
- El emparejamiento iónico en complejos catalíticos ofrece un mecanismo potencial para el control electrostático.
Objetivo del estudio:
- Investigar el impacto del emparejamiento iónico en la regioselectividad en la hidroarilación catalizada por oro.
- Comprender cómo la proximidad de la contraparte influye en la energía del estado de transición y en la distribución del producto.
- Explorar el papel del dieléctrico del disolvente en la modulación de los efectos de emparejamiento de iones.
Principales métodos:
- Estudio experimental de la hidroarilación de los éteres de fenil propargilo sustituidos por 3 utilizando catalizadores catiónicos Au.
- Variación sistemática del dieléctrico del disolvente para controlar el emparejamiento de iones con los contraiones SbF6.
- Cálculos de la Teoría Funcional de Densidad (DFT) para determinar las diferencias de energía del estado de transición (ΔΔE‡).
Principales resultados:
- La regioselectividad de la formación de 2H-cromeno cambió hasta en un factor de 12 con el dieléctrico del disolvente variable.
- Los cálculos de DFT predijeron con precisión los cambios de selectividad experimental mediante el análisis de Δ(ΔΔE‡).
- El emparejamiento iónico estabiliza preferentemente los estados de transición con una mayor separación de cargas.
Conclusiones:
- El emparejamiento de iones con contraiones puede utilizarse eficazmente para controlar la regioselectividad en la catálisis.
- El dieléctrico del disolvente juega un doble papel: forzar el emparejamiento de iones e influir en las interacciones complejas con el disolvente.
- Este trabajo proporciona un marco para el diseño de sistemas catalíticos selectivos basados en el control electrostático.
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