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Epoxidación asimétrica catalítica de enonas utilizando el complejo de óxido de La-BINOL-trifenilarsina: determinación
T Nemoto1, T Ohshima, K Yamaguchi
1Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
Journal of the American Chemical Society
|July 18, 2001
Resumen
Un nuevo complejo de óxido de lantano-BINOL-trifenilarsina cataliza eficientemente la epoxidación asimétrica de las enonas. Este método produce cetonas epoxi con altos rendimientos y enantioselectividades, ofreciendo información sobre los mecanismos catalíticos.
Área de la Ciencia:
- Química organometálica Química orgánica de los metales.
- Catalización asimétrica por catálisis asimétrica.
- Síntesis orgánica La síntesis orgánica.
Sus antecedentes:
- La epoxidación de enonas es una transformación crucial en la síntesis orgánica.
- El desarrollo de catalizadores de epoxidación asimétricos eficientes y selectivos sigue siendo un desafío clave.
- Los catalizadores basados en lantanoides ofrecen propiedades únicas de acidez y coordinación de Lewis.
Objetivo del estudio:
- Para describir la epoxidación asimétrica catalítica de las enonas utilizando un nuevo complejo La-BINOL-Ph(3)As=O.
- Para aclarar la estructura y las especies activas del sistema catalítico.
- Proponer un mecanismo de reacción y comprender el papel del isopropoxido de lantano.
Principales métodos:
- Preparación del complejo La-BINOL-Ph ((3) As=O a partir del lantano ((III) isopropoxido, el BINOL y el óxido de trifenilarzina.
- Epoxidación asimétrica catalítica de varios enones utilizando 1-5 mol % del catalizador.
- Caracterización estructural utilizando análisis de la estructura cristalina de rayos X.
Principales resultados:
- El sistema catalizador epoxidó eficientemente una gama de enonas, incluidas las dienonas y las cis-enonas.
- Se lograron altos rendimientos (hasta el 99%) y excelentes enantioselectividades (hasta >99% ee).
- Se determinó la estructura del complejo activo La-BINOL-Ph ((3) As=O, lo que representa el primer análisis de rayos X de un complejo lantanoide-BINOL libre de metales alcalinos.
Conclusiones:
- El complejo La-BINOL-Ph ((3) As=O es un catalizador muy eficaz para la epoxidación asimétrica de enonas.
- El estudio proporciona conocimientos mecanicistas, incluida la función de la formación de complejos heteroquirales en la amplificación asimétrica.
- El isopropoxido de lantano acelera la reacción mientras mantiene una alta enantioselectividad.
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