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Hidroxilaciones alifáticas de C-H dirigidas a metales (oxo): el sesgo de sustrato predominante
Marinus A Bigi1, Sean A Reed, M Christina White
1Department of Chemistry, Roger Adams Laboratory, University of Illinois, Urbana, Illinois 61801, USA.
Journal of the American Chemical Society
|May 22, 2012
Resumen
Una nueva estrategia de dirección utiliza grupos de ácido carboxílico para guiar las hidroxilaciones C-H catalizadas por metales. Este enfoque supera los sesgos inherentes, permitiendo una oxidación precisa de moléculas complejas como el paclitaxel.
Área de la Ciencia:
- Química organometálica Química orgánica de los metales.
- Síntesis orgánica La síntesis orgánica.
- La catálisis de la catálisis.
Sus antecedentes:
- La hidroxilación C-H es una transformación crucial en la síntesis orgánica.
- Los complejos de hierro no hemo ofrecen una actividad catalítica prometedora, pero se enfrentan a desafíos con la selectividad debido a factores electrónicos y estéricos.
- Los grupos de dirección a menudo son necesarios para lograr la funcionalización específica del sitio.
Objetivo del estudio:
- Describir la primera estrategia general para un efecto de dirección en las hidroxilaciones C-H promovidas por metales (oxo).
- Para demostrar cómo las fracciones de ácido carboxílico pueden superar los sesgos desfavorables en las hidroxilaciones C-H catalizadas por hierro.
- Para permitir la oxidación específica del sitio en complejos marcos de productos naturales.
Principales métodos:
- Utilizó un complejo de hierro no hemo, Fe (PDP), como catalizador.
- Sustratos empleados que contienen grupos funcionales de ácido carboxílico como fracciones directivas.
- Investigó la oxidación C-H del marco de paclitaxel para demostrar el efecto de dirección.
Principales resultados:
- Los grupos de ácido carboxílico dirigieron con éxito la hidroxilación C-H, superando los sesgos electrónicos, estéricos y estereoelectrónicos.
- El efecto de dirección desvió la oxidación lejos de una vía C-1 favorecida en el paclitaxel.
- Se logró la instalación de la oxidación C-2 con el estado de oxidación natural y la estereoconfiguración en el paclitaxel.
Conclusiones:
- Se ha establecido una estrategia general para dirigir las hidroxilaciones C-H promovidas por metales (oxo) utilizando ácidos carboxílicos.
- Esta metodología proporciona una poderosa herramienta para controlar la selectividad del sitio en las reacciones de funcionalización C-H desafiantes.
- El enfoque permite la síntesis de moléculas complejas, ejemplificada por la oxidación selectiva del paclitaxel.
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