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Reacciones contrastantes de cetonas y tioketonas con alquillitios: una investigación experimental y computacional
William F Bailey1, Ashley L Bartelson, Kenneth B Wiberg
1Department of Chemistry, University of Connecticut, Storrs, Connecticut 06269-3060, USA. william.bailey@uconn.edu
Journal of the American Chemical Society
|January 17, 2012
Resumen
Las reacciones del organolitio con las tioketonas difieren significativamente de las de las cetonas. Mientras que las cetonas se someten a adición, las tioketonas como la adamantantanetiona producen principalmente tiolos debido al azufre.
Área de la Ciencia:
- Química orgánica es la química orgánica.
- Química organometálica Química orgánica de los metales.
Sus antecedentes:
- Las reacciones de cetonas con organolitios típicamente implican la adición nucleofílica al grupo carbonilo.
- Las reacciones de tiocetona con los organolitios son menos conocidas y producen diversos productos, con adiciones menores.
Objetivo del estudio:
- Investigar exhaustivamente las reacciones de los organolitios con el adamantantanetión.
- Para aclarar las diferencias mecánicas entre las reacciones de cetona y tiocetona con organolitios.
Principales métodos:
- Se han estudiado las reacciones de la adamantantanetiona con metilo, n-butilo y tert-butilolithium.
- Modelado computacional empleado (B3LYP/6-311+G*) para analizar estados de transición para reacciones de adición y reducción.
- Utilizó acetona y tioacetona como sustratos modelo para el análisis computacional.
Principales resultados:
- Las reacciones de adamantantanetiona con n-butilitio y tert-butilitio producen predominantemente el 2-adamantanetiol.
- Los estudios computacionales revelaron estados de transición distintos para la adición de organolitio a los enlaces C=O vs. C=S, lo que explica la adición más lenta a las tioketonas.
- La reducción de tioketonas por organolitios es más exotérmica con menor energía de activación en comparación con las cetonas.
Conclusiones:
- Las propiedades electrónicas y estéricas únicas del azufre divalente influyen en la reactividad del organolitio con las tioketonas.
- Las vías de reacción de las tioketonas y cetonas con los organolitios divergen significativamente debido a las diferencias en la energía y geometría del estado de transición.
- Las vías mediadas por radicales también pueden desempeñar un papel en estas reacciones.
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