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Alquilación catalítica de enlaces C-H remotos habilitados por la transferencia de electrones acoplados a protones

Gilbert J Choi¹, Qilei Zhu^1,1, David C Miller¹

¹Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA.

|October 13, 2016

Resumen

Los investigadores desarrollaron un nuevo método catalítico para romper los fuertes enlaces nitrógeno-hidrógeno en amidas utilizando la transferencia de electrones acoplados a protones. Esto permite la formación directa de enlaces carbono-carbono, simplificando la síntesis de moléculas que contienen aminas.

Área de la Ciencia:

Química orgánica
Fotocatálisis
La Química Radical

Sus antecedentes:

La catálisis de transferencia de átomos de hidrógeno (HAT) ha avanzado, pero carece de catalizadores moleculares para la homólisis de fuertes enlaces N-H en amidas N-alquilo.
La homólisis de amida produce radicales amidil cruciales para la aminación de olefinas y la funcionalización dirigida de C-H (reacción de Hofmann-Löffler-Freytag).
Los métodos existentes requieren N-prefuncionalización, limitando la construcción directa de enlaces C-C e incorporando grupos de activación en los productos.

Objetivo del estudio:

Desarrollar un nuevo protocolo catalítico para la homólisis directa de enlaces NH en amidas N-alquilo no activadas.
Permitir la generación de radicales amídicos a partir de amidas simples para las transformaciones sintéticas posteriores.
Establecer una variante catalítica de la reacción de Hofmann-Löffler-Freytag para la formación directa de enlaces C-C.

Principales métodos:

Utilizando un fotocatalizador de iridio en estado excitado y una base de fosfato débil.
Utilizando la transferencia de electrones acoplados a protones (PCET) para la eliminación concertada de protones y electrones del enlace N-H de la amida.
Demostrando la capacidad de los radicales amídicos generados para realizar la abstracción C-H y la alquilación radical.

Principales resultados:

Homólisis exitosa de enlaces N-H en amidas N-alquilo a través de PCET, superando las limitaciones de la catálisis HAT tradicional.
Generación de radicales amidil intermedios capaces de promover la abstracción de C-H.
Alquilación catalítica C-H de enlaces alifáticos C-H no activados utilizando amidas simples, formando nuevos enlaces C-C.

Conclusiones:

Un nuevo método catalítico permite la formación directa de enlaces C-C a partir de amidas simples a través de la alquilación de tipo C-H de Hofmann-Löffler-Freytag.
La transferencia de electrones acoplados a protones facilita la activación homolítica de enlaces N-H energéticamente inaccesibles.
Este enfoque simplifica la síntesis y la elaboración de compuestos que contienen aminas prevalentes en productos farmacéuticos y naturales.

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