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Preparation and Use of Samarium Diiodide (SmI2) in Organic Synthesis: The Mechanistic Role of HMPA and Ni(II) Salts in the Samarium Barbier Reaction
Published on: February 4, 2013
Estudios sobre el mecanismo, la selectividad y la utilidad sintética de la reducción de la lactona utilizando SmI(2)
Dixit Parmar1, Lorna A Duffy, Dhandapani V Sadasivam
1School of Chemistry, University of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom.
Journal of the American Chemical Society
|September 22, 2009
Resumen
El diioduro de samario activado con agua (SmI(2) ahora puede reducir ésteres simples y lactonas. Este nuevo sistema SmI(2)-H(2)O reduce selectivamente las lactonas de seis miembros y permite ciclizaciones diastereoselectivas.
Área de la Ciencia:
- Química orgánica es la química orgánica.
- Química sintética de la química sintética.
- Química de los Lantánidos
Sus antecedentes:
- Anteriormente se consideraba que los ésteres y las lactonas eran resistentes a la reducción por el diioduro de samario (SmI(2)).
- Los nuevos métodos de activación son cruciales para expandir la utilidad sintética de los reactivos lantánidos.
Objetivo del estudio:
- Para investigar la reducción de ésteres y lactonas utilizando SmI(2) activado por agua.
- Explorar la selectividad y las vías mecanicistas de este nuevo sistema de reducción.
- Para utilizar los radicales intermedios generados para posteriores transformaciones sintéticas.
Principales métodos:
- Activación de SmI(2) con cantidades controladas de agua (H(2) O).
- Espectrofotometría de flujo detenido para estudios cinéticos.
- Análisis experimentales y computacionales para elucidar los mecanismos de reacción.
- Reacciones de ciclización radical para formar cetonas o cetalos cíclicos.
Principales resultados:
- El sistema SmI(2)-H(2)O reduce eficazmente los ésteres alifáticos simples y las lactonas.
- Se observó una selectividad completa para la reducción de las lactonas de seis miembros sobre otras lactonas y ésteres.
- Los radicales intermedios se emplearon con éxito en las reacciones de ciclización, produciendo productos cíclicos con alta diastereoselectividad.
- Estas ciclizaciones representan los primeros casos de ciclizaciones de radicales éster-alqueno utilizando el éster carbonilo como equivalente del radical acilo.
Conclusiones:
- La activación del agua desbloquea el poder reductor de SmI para los ésteres y las lactonas.
- El sistema SmI(2)-H(2)O ofrece un método selectivo y potente para la reducción de la lactona.
- Esta metodología proporciona una nueva ruta para la síntesis diastereoselectiva de compuestos cíclicos a través de ciclizaciones de radicales éster-alqueno.
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