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Mecanismo y estructuras de estado de transición para reacciones de acoplamiento reductivo alquino-aldehído

P R McCarren¹, Peng Liu, Paul Ha-Yeon Cheong

¹Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, USA.

Journal of the American Chemical Society

|April 29, 2009

Resumen

La teoría funcional de la densidad revela que el acoplamiento reductor catalizado por níquel de alquinas y aldehídos se produce a través de la ciclización oxidativa. Este mecanismo, estabilizado por d --> pi* retro-donación, es acelerado por los ácidos de Lewis que se coordinan con el aldehído.

Área de la Ciencia:

Química organometálica Química orgánica de los metales.
La catálisis de la catálisis.
Química computacional es la química computacional.

Sus antecedentes:

Las reacciones de acoplamiento catalizadas por níquel son vitales en la síntesis orgánica.
Comprender los mecanismos de reacción es clave para optimizar la eficiencia catalítica.

Objetivo del estudio:

Para dilucidar el mecanismo detallado del acoplamiento reductivo alquino-aldehído catalizado por níquel.
Identificar los principales intermediarios y estados de transición que rigen la reactividad y la selectividad.

Principales métodos:

Se emplearon cálculos de la Teoría Funcional de Densidad (DFT).
Análisis de las vías de reacción, productos intermedios y estados de transición.

Principales resultados:

El mecanismo preferido implica la ciclización oxidativa a un intermediario de nickeladihidrofurano.
El paso que determina la velocidad y la selectividad es el estado de transición de ciclización oxidativa.
d --> pi*(perpendicular) la retro-donación estabiliza el estado de transición, favoreciendo las alquinas sobre los alquenos.
Los ácidos de Lewis aceleran la reacción coordinándose con el oxígeno aldehído.

Conclusiones:

El estudio proporciona una comprensión mecanicista detallada del acoplamiento reductivo alquino-aldehído catalizado por níquel.
Los hallazgos ofrecen ideas para diseñar sistemas catalíticos más eficientes.

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