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Ciclizaciones enantioselectivas de cola a cabeza catalizadas por donantes de doble enlace de hidrógeno
Dennis A Kutateladze1, Daniel A Strassfeld1, Eric N Jacobsen1
1Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, United States.
Journal of the American Chemical Society
|April 1, 2020
Resumen
Los derivados de urea quiral catalizan las ciclizaciones enantioselectivas. Un mecanismo cooperativo que involucra dos moléculas catalizadoras y la participación de la olefina π explica la estabilización selectiva del estado de transición y la alta enantioselectividad.
Área de la Ciencia:
- Química orgánica
- Catálisis
- Síntesis asimétrica
Sus antecedentes:
- Los derivados de urea quiral son catalizadores valiosos en la síntesis orgánica.
- Las reacciones de ciclización enantioselectivas son cruciales para la construcción de moléculas complejas.
- El control de las vías de reacción para favorecer la ciclización sobre la eliminación es un desafío clave.
Objetivo del estudio:
- Investigar la actividad catalítica de los derivados quirales de urea en las reacciones de ciclización de cola a cabeza.
- Aclarar el mecanismo de reacción, incluida la participación de la olefina π y la cooperación del catalizador.
- Para lograr una alta enantioselectividad en la ciclización de los análogos del cloruro de nerilo.
Principales métodos:
- Síntesis y aplicación de catalizadores de urea quiral.
- Estudios cinéticos experimentales para determinar las velocidades y órdenes de reacción.
- Estudios computacionales (por ejemplo, DFT) para modelar estados de transición y vías de reacción.
- Análisis de los productos de ciclización de los análogos del cloruro de nerilo.
Principales resultados:
- Los derivados de urea quiral catalizaron efectivamente la ciclización enantioselectiva de la cola a la cabeza.
- Los datos experimentales apoyaron un mecanismo que involucra la participación de la olefina π, facilitando la ionización del cloruro.
- Los estudios cinéticos y computacionales revelaron un modo catalítico cooperativo con dos moléculas de urea que estabilizan el estado de transición.
- Se logró una alta enantioselectividad, con vías que evitan la eliminación simple.
Conclusiones:
- Los derivados de urea quiral son catalizadores eficientes para las ciclizaciones enantioselectivas.
- Un mecanismo cooperativo que implique la activación del sustrato y la estabilización del estado de transición es clave para el enantiocontrol.
- El estudio proporciona información sobre el diseño de nuevos catalizadores para la síntesis asimétrica.
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