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Mecanismo de la hidrogenación de transferencia catalizada por Pd ((NHC) de los alquinos

Peter Hauwert¹, Romilda Boerleider, Stefan Warsink

¹Molecular Inorganic Chemistry, Van't Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, Postbus 94157, 1090 GD Amsterdam, The Netherlands.

Journal of the American Chemical Society

|November 10, 2010

Resumen

Este estudio presenta un método altamente selectivo para la conversión de alquinos en (Z) -alquenos utilizando un catalizador de paladio y formato. La investigación aclara el mecanismo de reacción, destacando las etapas de transferencia de protones e hidruro que determinan la velocidad por separado.

Área de la Ciencia:

Química organometálica Química orgánica de los metales.
La catálisis es la catálisis.
Síntesis orgánica La síntesis orgánica.

Sus antecedentes:

La semihidrogenación de los alquinos a (Z) -alquenos es una transformación crucial en la síntesis orgánica.
Lograr una alta quimio y estereoselectividad en esta reacción sigue siendo un desafío.

Objetivo del estudio:

Desarrollar un sistema catalítico altamente selectivo para la semihidrogenación de alquinos.
Para aclarar el mecanismo de reacción y entender los orígenes de la selectividad.

Principales métodos:

Utilizó un complejo de palladio ((NHC) ((anhidrido maleico) como un precatalizador.
Formato de trietilamonio empleado como el donante de hidrógeno.
Se llevaron a cabo estudios de etiquetado cinético y de deuterio.
Se monitoreó la reacción utilizando espectroscopia de RMN.

Principales resultados:

Logró una excelente quimio- y estereoselectividad en la semihidrogenación de transferencia de alquinas a (Z) -alquenos.
Los estudios cinéticos revelaron una dependencia de orden complejo sobre el sustrato y una dependencia de primer orden sobre el catalizador y el donante de hidrógeno.
El etiquetado de deuterio indicaba pasos separados de transferencia de protones e hidruro que determinaban la velocidad.
El monitoreo de RMN confirmó la presencia de formatos coordinados e intermediarios de anhídrido maleico.

Conclusiones:

Propuso un mecanismo detallado que involucra la transferencia de hidrógeno desde el formato coordinado, la inserción migratoria y la protonólisis.
La alta selectividad se atribuye a la competencia entre el disolvente y el alquino por un intermediario de paladio (alqueno).

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