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Imine Metathesis by Silica-Supported Catalysts Using the Methodology of Surface Organometallic Chemistry
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Formación concertada de enlaces C-N y C-H en una hidroaminación catalizada por magnesio
James F Dunne1, D Bruce Fulton, Arkady Ellern
1Department of Chemistry and U.S. Department of Energy Ames Laboratory, Iowa State University, Ames, Iowa 50011, United States.
Journal of the American Chemical Society
|December 2, 2010
Resumen
Un precatalizador de magnesio facilita la hidroaminación y la ciclización intramoleculares. La reacción procede a través de un estado de transición de dos sustratos, con la asociación catalizador-sustrato que precede al paso de ciclización que limita la velocidad.
Área de la Ciencia:
- Química organometálica de las sustancias orgánicas.
- La catálisis de la catálisis.
- La síntesis orgánica es la síntesis orgánica.
Sus antecedentes:
- La hidroaminación intramolecular es una reacción clave en la síntesis orgánica.
- El desarrollo de precatalizadores eficientes para tales transformaciones es crucial.
- La comprensión de los mecanismos de reacción es esencial para la optimización del catalizador.
Objetivo del estudio:
- Para investigar la actividad catalítica de un complejo de magnesio saturado coordinadamente.
- Para dilucidar el mecanismo de la hidroaminación / ciclización intramolecular.
- Para identificar el paso limitador de velocidad en el ciclo catalítico.
Principales métodos:
- Síntesis y caracterización del precatalizador de magnesio, To(M) MgMe.
- Estudios cinéticos para determinar la ley de velocidad y el orden de reacción.
- Aislamiento y estudio del estado de reposo del catalizador.
- Propuesta mecánica basada en observaciones experimentales.
Principales resultados:
- El complejo de magnesio To(M) MgMe es un precatalizador activo para la hidroaminación/ciclización intramolecular a 50 °C.
- La reacción sigue la cinética de Michaelis-Menten, lo que indica una asociación reversible entre catalizador y sustrato.
- El estado de reposo aislable (amidoalqueno de magnesio) no cicliza unimolecularmente, sino que se activa mediante la adición de sustrato.
- Se propone un estado de transición de dos sustratos y seis centros para el paso de limitación de la rotación.
Conclusiones:
- El ciclo catalítico implica una asociación inicial reversible del sustrato con el catalizador de magnesio.
- El paso de limitación de la rotación es un proceso concertado dentro de un estado de transición de seis centros propuesto.
- Este estudio proporciona conocimientos mecanicistas sobre las reacciones de hidroaminación / ciclización catalizadas por magnesio.
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