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Estudios mecánicos sobre una alquilación alilica asimétrica catalizada por Cu con materiales de partida racémicos
Emeline Rideau1, Hengzhi You1, Mireia Sidera1
1Department of Chemistry, Chemistry Research Laboratory, University of Oxford , 12 Mansfield Road, Oxford, OX1 3TA, U.K.
Journal of the American Chemical Society
|April 1, 2017
Resumen
Los catalizadores de cobre facilitan las adiciones asimétricas a los haluros alílicos formando especies oligoméricas complejas. Estos catalizadores racemizan los materiales de partida y producen selectivamente un enantiómero para transformaciones asimétricas dinámicas.
Área de la Ciencia:
- Química organometálica
- Catálisis asimétrica
Sus antecedentes:
- Las reacciones asimétricas catalizadas por cobre son cruciales para sintetizar moléculas quirales.
- Comprender los mecanismos de estas reacciones, especialmente las transformaciones cinéticas asimétricas dinámicas, es clave para desarrollar nuevos sistemas catalíticos.
Objetivo del estudio:
- Elucidar el mecanismo de las adiciones asimétricas catalizadas por Cu a los electrofilos alilicos racémicos.
- Investigar el papel de los complejos oligoméricos de ligando de cobre y de los contraiones en la catálisis.
- Desarrollar nuevas condiciones de reacción y ligandos para mejorar la enantioselectividad y el alcance del sustrato.
Principales métodos:
- Estudios mecánicos que incluyen el etiquetado isotópico, la espectroscopia de RMN (cinética y dinámica) y el modelado cinético.
- Análisis de la relación estructura-actividad y desarrollo de nuevos ligandos de fosforamidita.
- Investigación de los compuestos intermedios de yoduro de alilo y cloruro de alilo.
Principales resultados:
- Los complejos oligoméricos de Cu-ligando evolucionan durante la reacción, mejorando la velocidad y la enantioselectividad.
- Los cu-conteriones influyen en la selección de la vía y la racemicidad a través de intermediarios de yoduro de alilo.
- El nuevo ligando D permite una adición altamente enantioselectiva a los fosfatos alilicos racémicos y a los cloruros de alilo de siete anillos.
Conclusiones:
- El mecanismo propuesto implica catalizadores oligoméricos complejos que racemizan sustratos y logran una alta enantioselectividad.
- Este trabajo proporciona información sobre el desarrollo de transformaciones asimétricas dinámicas de manera más amplia.
- Se espera que los hallazgos faciliten la extensión de las reacciones asimétricas catalizadas por cobre.
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