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Alto rendimiento de los catalizadores Rh ((Phebox) en la reacción asimétrica reductora de aldol: alta

Hisao Nishiyama¹, Takushi Shiomi, Yasunori Tsuchiya

¹Department of Applied Chemistry, Graduate School of Engineering, Nagoya University, Chikusa, Nagoya 464-8603, Japan. hnishi@apchem.nagoya-u.ac.jp

Journal of the American Chemical Society

|May 12, 2005

Resumen

Los catalizadores de rodio quiral permiten reacciones de aldol reductoras asimétricas eficientes. El proceso produce beta-hidroxipropionatos con alta anti y enantioselectividad, probablemente a través de un estado de transición cíclico.

Área de la Ciencia:

Química orgánica es la química orgánica.
La catálisis de la catálisis.
Síntesis asimétrica de síntesis.

Sus antecedentes:

La reacción asimétrica reductora de aldol es crucial para la síntesis de moléculas quirales.
El desarrollo de sistemas catalíticos eficientes para esta transformación sigue siendo un desafío importante en la química orgánica.

Objetivo del estudio:

Desarrollar un sistema catalítico altamente selectivo para la reacción asimétrica reductora de aldol.
Para investigar el mecanismo y el resultado estereoquímico de la reacción.

Principales métodos:

Se utilizan complejos quirales de rodio ((bisoxazolinylphenyl) como catalizadores (1 mol %).
Empleó varios aldehídos, ésteres alfa y beta insaturados e hidrosilanos como sustratos.
Reacciones realizadas a 50 grados C durante 0,5-1,0 horas.

Principales resultados:

Se logró una catálisis eficiente para la reacción asimétrica reductora de aldol.
Se obtienen beta-hidroxipropionatos con una excelente anti-selectividad (hasta el 98%) y enantioselectividad (hasta el 96% ee).
Propuso un estado de transición cíclico parecido a una silla que involucra un intermediario de rodio-E-enolato para explicar el resultado estereoquímico.

Conclusiones:

Los complejos de quiral rodio ((bisoxazolinylphenyl) son catalizadores muy efectivos para las reacciones asimétricas reductoras de aldol.
El método desarrollado proporciona una ruta fácil a los beta-hidroxipropionatos enriquecidos enantioméricamente.
El modelo de estado de transición propuesto racionaliza la alta estereoselectividad observada.

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