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Cinética contraintuitiva en la alilación Tsuji-Trost: partición de pares iónicos e implicaciones para la catálisis
Louise A Evans1, Natalie Fey, Jeremy N Harvey
1University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK.
Journal of the American Chemical Society
|October 9, 2008
Resumen
Los ligandos de fosfina donantes de electrones aceleran las reacciones de alilación catalizadas por el paladio. La adición de tetra (bis-3,5-trifluoromethyl) fenilborato de sodio aumenta las velocidades de reacción y la inducción asimétrica en la alilación Tsuji-Trost.
Área de la Ciencia:
- Química organometálica Química orgánica de los metales.
- La catálisis de la catálisis.
- Síntesis orgánica La síntesis orgánica.
Sus antecedentes:
- La alilación Tsuji-Trost catalizada por el paladio es una reacción clave en la síntesis orgánica.
- El mecanismo de reacción involucra intermediarios electrofílicos de paladio y alilo.
- La elección de ligandos influye significativamente en la actividad catalítica y la selectividad.
Objetivo del estudio:
- Para investigar la cinética de la alilación de Tsuji-Trost catalizada por el paladio con varios ligandos de fosfina.
- Para aclarar el papel de las propiedades electrónicas de los ligandos en las tasas de reacción.
- Para explorar el impacto de los efectos de contrarión en el volumen de negocios catalítico y la inducción asimétrica.
Principales métodos:
- Estudios cinéticos de las reacciones de alilación catalizadas por el paladio.
- Variación sistemática de las propiedades electrónicas de los ligandos de fosfina.
- La inclusión de tetra (bis-3,5-trifluorometil) fenilborato de sodio catalítico (NaBAr'F) también está incluida.
- Análisis de la enantioselectividad utilizando cromatografía quiral.
Principales resultados:
- El aumento de la capacidad de donación de electrones de los ligandos de fosfina aumentó las tasas de reacción, contrariamente a las hipótesis iniciales.
- NaBAr'F atenuó el retorno de pares de iones, lo que lleva a una aceleración significativa de la tasa.
- La inducción asimétrica mejoró del 28% al 78% con el ligando BINAP en presencia de NaBAr'F.
Conclusiones:
- Los efectos electrónicos ligandos y las interacciones conteriones juegan un papel crucial en la cinética de la alilación Tsuji-Trost.
- El uso de la cocatálisis [M]n+([BAr'F]-) n ofrece una estrategia prometedora para optimizar las reacciones catalizadas por metales de transición.
- Este enfoque tiene amplia aplicabilidad en otros procesos catalíticos que involucran intermedios iónicos.
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