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El catalizador no simétrico de quiral en rutenio para la amidación intramolecular enantioselectiva altamente
Zijun Zhou1, Shuming Chen2, Yubiao Hong1
1Fachbereich Chemie , Philipps-Universität Marburg , Hans-Meerwein-Strasse 4 , 35043 Marburg , Germany.
Journal of the American Chemical Society
|November 22, 2019
Resumen
Los nuevos catalizadores quirales de rutenio con ligandos de carbenos N-heterocíclicos remotos permiten una amidación intramolecular eficiente. Los catalizadores no simétricos de C2 producen gamma-lactamas quirales con alta enantioselectividad, que superan a las contrapartes simétricas de C2.
Área de la Ciencia:
- Química organometálica
- Catálisis
- Síntesis asimétrica
Sus antecedentes:
- Los catalizadores de rutenio son cruciales en la síntesis orgánica.
- Los catalizadores quirales permiten las transformaciones enantioselectivas.
- Los carbenos N-heterocíclicos (NHC) son ligandos versátiles en la catálisis.
Objetivo del estudio:
- Para introducir una nueva clase de catalizadores de rutenio quiral.
- Investigar la actividad catalítica de estos complejos en la amidación intramolecular C ((sp3) -H.
- Para entender el papel de la estereoquímica centrada en el metal en los resultados catalíticos.
Principales métodos:
- Síntesis de complejos quirales de rutenio con ligandos N-heterocíclicos remotos de piridilideno (rNHC).
- Pruebas catalíticas de la amidación intramolecular C ((sp3) -H de las 1,4,2-dioxazol-5-onas.
- Determinación de las relaciones enantioméricas mediante cromatografía quiral.
- Cálculos de la Teoría Funcional de la Densidad (DFT) para elucidar los mecanismos de reacción.
Principales resultados:
- Se sintetizó una nueva clase de catalizadores quirales de rutenio ciclometalizados por heterociclos de 7-metil-1,7-fenantrolinio.
- Los complejos quirales en rutenio no simétricos con C2 exhibieron una alta actividad catalítica para la amidación intramolecular C ((sp3) -H, produciendo gamma-lactamas quirales con hasta 99:1 er.
- Las cargas de catalizador tan bajas como 0,005 mol % fueron efectivas (hasta 11,200 TON).
- Los diastereómeros simétricos C2 fueron sometidos predominantemente a reordenamientos no deseados de tipo Curtius.
- Los cálculos de DFT revelaron los orígenes de la reactividad superior de los catalizadores no simétricos C2.
Conclusiones:
- La estereoquímica relativa centrada en el metal es crítica para lograr una alta enantioselectividad en la amidación C ((sp3) -H.
- Los catalizadores de rutenio quiral no simétricos con C2 ofrecen una eficiencia sin precedentes para sintetizar gamma-lactamas quirales.
- El sistema catalítico desarrollado proporciona una herramienta valiosa para la síntesis asimétrica.
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