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Manejo de sustratos altamente coordinados en catálisis asimétrica: una aminación asimétrica catalítica con un
Tomoyuki Mashiko1, Naoya Kumagai, Masakatsu Shibasaki
1Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan.
Journal of the American Chemical Society
|September 30, 2009
Resumen
Un nuevo catalizador de lantano/amida permite la aminación asimétrica de sustratos difíciles como las succinimidas y las alfa-alcoxicarboniloamidas con alto rendimiento y enantioselectividad. Este avance ofrece nuevas posibilidades en la catálisis asimétrica.
Área de la Ciencia:
- Química orgánica es la química orgánica.
- La catálisis de la catálisis.
- Síntesis asimétrica de síntesis.
Sus antecedentes:
- La aminación asimétrica catalítica es crucial para la síntesis de moléculas quirales.
- El desarrollo de catalizadores eficientes para sustratos difíciles sigue siendo un objetivo clave en la síntesis orgánica.
Objetivo del estudio:
- Desarrollar un nuevo sistema de catalizador basado en lantano/amida para la aminación asimétrica.
- Para investigar el rendimiento catalítico y el mecanismo para desafiar sustratos.
Principales métodos:
- Utilizado el hexahidrato de nitrato de lantano, (R)-3a, y H-d-Val-O(t) Bu como el sistema catalizador.
- Empleó análisis espectroscópicos, experimentos de control y estudios cinéticos para la investigación mecanicista.
- Se aplicó el catalizador a la aminación asimétrica de los derivados de la succinimida y las amidas alfa-alcoxicarbonilo N-no sustituidas.
Principales resultados:
- Se logró una aminación asimétrica catalítica del derivado 1 de succinimida no protegido con una carga de catalizador de 1 mol %.
- Eficacia demostrada para amidas alfa-alcoxicarbonilo N-no sustituidas sin precedentes, dando productos con hasta >99% de rendimiento y >99% de exceso enantiomérico (ee).
- Se identificó un complejo ternario que involucra a La(NO(3))(3)*6H(2)O/(R)-3a/H-d-Val-O(t) Bu como la probable especie activa.
Conclusiones:
- El sistema de catalizador de lantano/amida exhibe un alto rendimiento catalítico y enantiocontrol.
- La activación del sustrato a través de la coordinación del lantano y el enlace cooperativo de hidrógeno en el estado de transición son clave para el éxito de la reacción.
- Este método expande el alcance de la aminación asimétrica a sustratos previamente inaccesibles.
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