Termodinámica ceto-enol de los intermediarios de Breslow
Mathias Paul1, Martin Breugst1, Jörg-Martin Neudörfl1
1Department of Chemistry (Organic Chemistry), University of Cologne , Greinstrasse 4, 50939 Cologne, Germany.
Journal of the American Chemical Society
|February 16, 2016
Resumen
Los investigadores sintetizaron los tautómeros ceto de los intermediarios de Breslow, que son clave en la catálisis de carbenos. Los efectos de sustitución sobre los aldehídos y los carbenos N-heterocíclicos influyen en la estabilidad de las formas enol versus ceto, revelando limitaciones cinéticas en la tautomerización.
Área de la Ciencia:
- Química orgánica
- Catálisis
- Química Física
Sus antecedentes:
- Los intermediarios de Breslow son cruciales en las reacciones umpolung catalizadas por carbenos.
- En trabajos anteriores se aislaron especies de aminoenol a partir de imidazolidinilidos y aldehídos.
- Los triazolidenos producen sólo tautómeros ceto con aldehídos, y carecen de enolos aislables.
Objetivo del estudio:
- Para sintetizar los tautómeros ceto de los diaminoenoles derivados del imidazolidinilideno.
- Para investigar la estabilidad termodinámica de los tautómeros enol-cetona.
- Comprender la influencia de los sustituyentes en la formación y estabilidad de los tautómeros.
Principales métodos:
- Síntesis de los tautómeros ceto.
- Análisis computacional de 15 pares de enol y cetona.
- Los cálculos termodinámicos.
Principales resultados:
- Se han sintetizado con éxito ceto tautómeros de diaminoenoles.
- Los sustituyentes de aldehído que retiran electrones favorecen la formación de enol.
- Los sustituyentes N,N'-Dipp y N,N'-Mes en los carbenos también favorecen la formación de enol.
- La sustitución de Dipp estabiliza el tautómero enol a través de interacciones dispersivas.
Conclusiones:
- Los efectos de sustitución dictan el equilibrio tautomérico enol-ceto.
- Los factores cinéticos, no sólo la termodinámica, pueden inhibir la tautomerización.
- Este trabajo aclara la naturaleza y la estabilidad de los tautómeros intermedios de Breslow.
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