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Cromo ((III) octaetilporfirinato tetracarbonilcobaltato: un catalizador muy activo, selectivo y versátil para la
Joseph A R Schmidt1, Emil B Lobkovsky, Geoffrey W Coates
1Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, USA.
Journal of the American Chemical Society
|August 11, 2005
Resumen
Un nuevo catalizador de porfirina de cromo permite una síntesis eficiente de las valiosas lactonas de los epoxidos. Este catalizador demuestra una alta actividad, selectividad y tolerancia del grupo funcional para las reacciones de carbonilación de epoxidos.
Área de la Ciencia:
- Química organometálica Química orgánica de los metales.
- La catálisis es la catálisis.
- Síntesis orgánica La síntesis orgánica.
Sus antecedentes:
- La carbonilación del epoxido es una transformación clave para la síntesis de lactonas.
- El desarrollo de catalizadores eficientes y selectivos sigue siendo un desafío.
Objetivo del estudio:
- Desarrollar un catalizador basado en porfirina altamente activo y selectivo para la carbonilación de epoxidos.
- Para sintetizar una amplia gama de lactonas sintéticamente útiles.
Principales métodos:
- Síntesis y caracterización del complejo [OEP) Cr (THF) 2) Co (CO) 4).
- Carbonilación catalítica de varios epóxidos bajo condiciones de reacción controladas.
- Análisis de la estereoquímica de la reacción para dilucidar los mecanismos.
Principales resultados:
- El catalizador [[[OEP]]Cr[[THF]]2][Co[[CO]]]] (1) exhibe excelentes números de rotación (hasta 10.000) y frecuencias (hasta 1670 h[[-1]]).
- La inserción regioselectiva de carbonilo ocurre en el menos obstaculizado carbono del epoxido.
- Alta tolerancia a diversos grupos funcionales, lo que permite la síntesis de varias lactonas alifáticas y cicloalifáticas.
- Producción exclusiva de isómeros de beta- o gamma-lactona lograda mediante el control de las condiciones de reacción.
Conclusiones:
- Un nuevo complejo de porfirina-cromo-cobalto cataliza eficientemente la carbonilación del epoxido.
- El catalizador facilita la síntesis rápida y selectiva de diversas lactonas.
- El mecanismo propuesto para la formación de gamma-lactona proporciona información sobre la estereoquímica de la reacción.
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