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Estudio mecanicista de las ciclizaciones reductivas nales catalizadas por níquel a través del análisis cinético
Ryan D Baxter1, John Montgomery
1Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109-1055, United States.
Journal of the American Chemical Society
|March 29, 2011
Resumen
Este estudio revela mecanismos de ciclización reductora catalizados por níquel. El silano se consume solo cuando están presentes el alquino y el aldehído, lo que sugiere un paso de ciclización oxidativa que determina la velocidad.
Área de la Ciencia:
- Química organometálica Química orgánica de los metales.
- La catálisis de la catálisis.
- Síntesis orgánica La síntesis orgánica.
Sus antecedentes:
- Las reacciones de ciclización reductiva son cruciales en la síntesis orgánica.
- La catálisis del níquel ofrece un enfoque versátil para formar compuestos cíclicos.
- La comprensión de los mecanismos de reacción es clave para optimizar las rutas sintéticas.
Objetivo del estudio:
- Para dilucidar el mecanismo de la ciclización reductora de níquel catalizado, mediado por silano de los ynals.
- Para determinar el paso que determina la velocidad y los intermedios involucrados en el ciclo catalítico.
Principales métodos:
- Se realizaron estudios cinéticos para evaluar los órdenes de reacción con respecto al catalizador de níquel, el sustrato de ynal y el reductor de silano.
- El análisis del consumo de silano en diversas condiciones de reacción proporcionó información sobre su papel.
Principales resultados:
- La reacción de ciclización demostró cinética de primer orden con respecto tanto a las concentraciones de níquel como de ynal.
- Se encontró que la reacción era de orden cero con respecto a la concentración de silano en la fase de iniciación.
- El consumo de silano se observó solo cuando las funcionalidades de alquina y aldehído estaban presentes en el sustrato.
Conclusiones:
- Los datos experimentales son inconsistentes con los mecanismos en los que la reacción se inicia a través de la adición oxidativa de Ni ((0) al silano.
- Un mecanismo plausible implica un paso de ciclización oxidativa que determina la velocidad y forma un ciclo metálico, seguido de una rápida reducción con silano.
- Esta comprensión mecanicista proporciona una base para el desarrollo de estrategias de ciclización reductora catalizadas por níquel.
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