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Los polihaloadamantanos pseudotetraédricos como sondas de quiralidad: síntesis, separación y configuración absoluta
Peter R Schreiner1, Andrey A Fokin, Oliver Lauenstein
1Institut für Organische Chemie der Justus-Liebig-Universität, Heinrich-Buff-Ring 58, D-35392 Giessen, Germany. prs@chem.uga.edu
Journal of the American Chemical Society
|November 7, 2002
Resumen
Los investigadores sintetizaron nuevos adamantanos halogenados utilizando la catálisis de transferencia de fase. El estudio demuestra una poderosa combinación de métodos experimentales y teóricos para asignar configuraciones absolutas, incluso en moléculas complejas.
Área de la Ciencia:
- Química orgánica es la química orgánica.
- La estereoquímica es la estereoquímica.
- La espectroscopia es una técnica de espectroscopia.
Sus antecedentes:
- Los hidrocarburos halogenados quirales estables son objetivos sintéticos valiosos.
- Asignar configuraciones absolutas de moléculas complejas puede ser un desafío.
Objetivo del estudio:
- Para sintetizar nuevos adamantanos halogenados conformacionalmente y configuracionalmente estables.
- Para separar y determinar las configuraciones absolutas de estos compuestos.
- Mostrar la utilidad de los métodos experimentales y computacionales combinados para la asignación estereoquímica.
Principales métodos:
- La halogenación catalítica de transferencia de fase para la síntesis.
- Cromatografía líquida de alto rendimiento (HPLC) en fases estacionarias quirales para la separación enantiomérica.
- Espectroscopia de dicroísmo circular (CD) (experimental y computacional) para la determinación de la configuración absoluta.
- Espectroscopia de Resonancia Magnética Nuclear (RMN) y cristalografía de rayos X para elucidación estructural.
Principales resultados:
- Se ha sintetizado con éxito 1-bromo-3-cloro-5-fluoro-adamantano y 1-bromo-3-cloro-5-fluoro-7-iodoadamantano.
- Se logró >99% de exceso enantiomérico (ee) para los antípodas ópticos del 1-bromo-3-cloro-5-fluoro-adamantano.
- El 1-bromo-3-cloro-5-fluoro-7-iodoadamantano representa el primer hidrocarburo alifático quiral que contiene todos los halógenos estables.
- Estructuras confirmadas usando RMN y cristalografía de rayos X.
- Demostró una asignación exitosa de configuración absoluta utilizando espectroscopia de CD, incluso para moléculas con rotación óptica débil y que carecen de cromóforos típicos.
Conclusiones:
- La catálisis por transferencia de fase es un método eficaz para la preparación de adamantanos halogenados complejos.
- La HPLC quiral y la espectroscopia de CD son potentes herramientas para la separación enantiomérica y la asignación de la configuración absoluta.
- La combinación de datos experimentales y cálculos teóricos proporciona una determinación estereoquímica robusta para moléculas difíciles.
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