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Sustitutos de binaftilo quirales axialmente con un enlace hidrógeno interno N-H-N
Takeo Kawabata1, Changsheng Jiang, Kazuhiro Hayashi
1Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan.
Journal of the American Chemical Society
|December 20, 2008
Resumen
Se sintetizaron nuevos sustitutos quirales binafílicos con fuertes enlaces de hidrógeno. Estos enantiómeros son estables a temperatura ambiente, separables por HPLC, y exhiben altas barreras de racemización, lo que indica aplicaciones potenciales en la síntesis asimétrica.
Área de la Ciencia:
- Química orgánica es la química orgánica.
- Química supramolecular de las moléculas.
Sus antecedentes:
- Los compuestos quirales binaftílicos son cruciales en la catálisis asimétrica.
- El desarrollo de nuevos andamios quirales con mayor estabilidad es de gran interés.
Objetivo del estudio:
- Para sintetizar y caracterizar nuevos sustitutos quirales binaftil con un enlace de hidrógeno intramolecular.
- Para investigar las barreras de estabilidad y racemización de estos nuevos compuestos quirales.
Principales métodos:
- Síntesis de nuevos sustitutos de binaftilo.
- Espectroscopia de Resonancia Magnética Nuclear (1H NMR) para confirmar la estructura y el enlace de hidrógeno.
- Cromatografía líquida de alto rendimiento (HPLC) con una fase estacionaria quiral para la separación enantiomérica.
- Estudios de racemicidad a temperatura ambiente para determinar la vida media y las energías de activación.
- Cristalografía de rayos X para elucidación estructural.
Principales resultados:
- Sintetizó con éxito nuevos sustitutos quirales de binaftil con fuertes enlaces de hidrógeno intramoleculares, evidenciados por cambios químicos de RMN de 1H (13,0-13,3 ppm).
- Los enantiómeros demostraron estabilidad a temperatura ambiente, con vidas medias de racemización que van desde 3 meses hasta 2 años.
- Se determinaron altas barreras de racemicidad (27.0-28.2 kcal/mol).
- HPLC separó con éxito los enantiómeros.
- El análisis de rayos X reveló un esqueleto de pseudonaftilo casi plano y un ángulo diédrico de 128 grados entre los anillos de pseudonaftaleno y naftaleno.
Conclusiones:
- Los sustitutos quirales de binaftilo diseñados exhiben una estabilidad excepcional debido a la fuerte unión de hidrógeno.
- Estos compuestos son candidatos prometedores para aplicaciones que requieren auxiliares quirales estables o ligandos en síntesis asimétrica.
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