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Hidrogenación asimétrica homogénea catalizada por Pd de indoles desprotegidos: estudios de alcance y mecanismos

Ying Duan¹, Lu Li, Mu-Wang Chen

¹State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences , Dalian 116023, China.

Journal of the American Chemical Society

|May 17, 2014

Resumen

Un nuevo método de hidrogenación asimétrica catalizado por paladio produce eficientemente indolinas quirales a partir de indolos no protegidos con alta enantioselectividad. Este avance permite una fácil síntesis de compuestos biológicamente activos y ofrece conocimientos mecanicistas sobre el proceso catalítico.

Área de la Ciencia:

Química orgánica es la química orgánica.
La catálisis de la catálisis.
Síntesis asimétrica de síntesis.

Sus antecedentes:

Los indoles son bloques de construcción cruciales en productos farmacéuticos y productos naturales.
La hidrogenación asimétrica de los indoles es un desafío, especialmente para sustratos desprotegidos.
El desarrollo de sistemas catalíticos eficientes para la síntesis quiral de indolina es altamente deseable.

Objetivo del estudio:

Desarrollar una hidrogenación asimétrica eficiente catalizada por paladio de indoles sin protección.
Para sintetizar productos biológicamente activos con un núcleo quiral de indolina.
Para dilucidar el mecanismo de reacción utilizando métodos experimentales y computacionales.

Principales métodos:

Hidrogenación asimétrica catalizada por paladio utilizando un fuerte activador de ácido de Brønsted.
Estudios de etiquetado de isótopos y ESI-HRMS para identificar los intermediarios de reacción.
Espectroscopia de RMN para observar las especies catalíticas activas.
Cálculos de la teoría funcional de la densidad (DFT) para la investigación mecanicista.

Principales resultados:

Se logra una alta enantioselectividad (hasta el 98% ee) en la hidrogenación de varios indolos no protegidos.
Se ha demostrado la fácil síntesis de derivados quirales de indolina biológicamente relevantes.
Se identificaron sales de iminio como productos intermedios clave y se observaron las especies activas de Pd-H.
Propuso un mecanismo de hidrogenación iónica y de esfera externa por etapas que involucraba un catalizador Pd bifuncional.

Conclusiones:

La metodología desarrollada proporciona una ruta eficiente a las indolinas quirales.
La reacción procede a través de un mecanismo único de hidrogenación iónica facilitado por un fuerte ácido de Brønsted y un disolvente polar.
La naturaleza bifuncional del catalizador y las interacciones de enlace de hidrógeno son cruciales para una alta enantioselectividad.
El proceso exhibe tolerancia al oxígeno, ácido y agua, lo que mejora su aplicabilidad práctica.

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