Un ácido de Lewis de silicio quiral simple y general para la síntesis asimétrica: cicloadiciones altamente
Seiji Shirakawa1, Pamela J Lombardi, James L Leighton
1Department of Chemistry, Columbia University, New York, New York 10027, USA.
Journal of the American Chemical Society
|July 14, 2005
Resumen
Un nuevo ácido de Lewis quiral silano permite una reacción de cicloadición [3 + 2] altamente selectiva. Este método práctico logra excelentes rendimientos y enantioselectividad, incluso a gran escala.
Área de la Ciencia:
- Química orgánica es la química orgánica.
- Síntesis asimétrica de síntesis.
Sus antecedentes:
- Las reacciones de cicloadición son fundamentales en la síntesis orgánica.
- El desarrollo de métodos enantioselectivos es crucial para la creación de moléculas quirales.
Objetivo del estudio:
- Para describir una nueva reacción de cicloadición, altamente diastereoselectiva y enantioselectiva [3 + 2].
- Para utilizar un simple quiral silano ácido de Lewis como catalizador.
Principales métodos:
- Empleando un ácido de Lewis silano quiral para mediar la [3 + 2] cicloadición entre las acilhidrazonas y los éteres de enol.
- Realización de reacciones a gran escala (5 g de hidrazona) para evaluar la viabilidad.
Principales resultados:
- Se logra una alta diastereoselectividad y enantioselectividad en la reacción de cicloadición.
- Se obtiene el producto con un rendimiento del 93% y un 99% de exceso enantiomérico (ee) después de la recristalización a gran escala.
- Proporcionó evidencia que apoya un mecanismo de reacción gradual y un modelo para la inducción asimétrica.
Conclusiones:
- La [3 + 2] cicloadición descrita es un método muy práctico y selectivo para sintetizar moléculas complejas.
- El quiral silano ácido de Lewis controla efectivamente la estereoquímica, ofreciendo una herramienta valiosa para la síntesis asimétrica.
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