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La alquilación catalítica C ((sp3) -H a través de un intermediario de carbeno de hierro
Jennifer R Griffin1, Chloe I Wendell1, Jacob A Garwin1
1Roger Adams Laboratory, Department of Chemistry, University of Illinois , Urbana, Illinois 61801, United States.
Journal of the American Chemical Society
|September 13, 2017
Resumen
Los investigadores desarrollaron un nuevo catalizador de ftalacianina de hierro para la alquilación de C ((sp3) -H, superando las limitaciones anteriores de los intermediarios de carbenos de hierro en la formación de enlaces C ((sp3) -C.
Área de la Ciencia:
- Química organometálica
- Catálisis
- Síntesis orgánica
Sus antecedentes:
- La funcionalización del enlace catalítico C ((sp3) -H es crucial para la construcción de moléculas.
- Los intermediarios de carbenos de hierro han mostrado históricamente un éxito limitado en la alquilación de C ((sp3) -H, favoreciendo otras reacciones como la ciclopropanación.
- Los catalizadores de hierro anteriores sobresalían en la oxidación y aminación de C ((sp3) -H, pero no en la alquilación a través de carbenos.
Objetivo del estudio:
- Desarrollar un sistema catalítico para la transformación del enlace C ((sp3) -H en C ((sp3) -C utilizando un intermediario de carbenos de hierro.
- Investigar el mecanismo de la alquilación de C ((sp3) -H mediada por carbenos de hierro.
- Demostrar la adaptabilidad del proceso catalítico mediante la modificación del catalizador.
Principales métodos:
- El complejo de ftaalocianina de hierro como catalizador.
- Alquilación de los enlaces alilico y bencílico C ((sp3) -H.
- Estudios mecánicos, incluido el análisis cinético y la caracterización intermedia.
Principales resultados:
- Se logró una alquilación catalítica exitosa de enlaces alílicos y bencílicos C ((sp3) -H utilizando un catalizador de ftaalocianina de hierro.
- Los estudios mecanicistas indicaron que un carbeno de hierro electrófilo media la escisión homolítica C-H.
- Se encontró que tanto la escisión de C-H como los pasos de rebote son ajustables, lo que sugiere que la escisión de C-H es parcialmente determinante de la velocidad.
Conclusiones:
- Los catalizadores de ftalacianina de hierro pueden mediar la alquilación de C ((sp3) -H a través de intermediarios de carbenos de hierro, una transformación previamente difícil de alcanzar.
- El mecanismo implica la escisión homolítica de C-H promovida por un carbeno de hierro electrófilo.
- El diseño del catalizador es clave para superar la inercia de los carbenos de hierro y promover la escisión C-H para una alquilación efectiva.
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