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Acoplamiento de naftol monitoreado por espectroscopia infrarroja en la fase gaseosa
1Department of Organic Chemistry, Charles University in Prague, Hlavova 8, 12843 Prague 2, Czech Republic. roithova@natur.cuni.cz
Journal of the American Chemical Society
|December 4, 2009
Resumen
El acoplamiento de naftol mediado por cobre ocurre en grupos binucleares de fase gaseosa. La irradiación desencadena el acoplamiento C-C, impulsado por la tautomerización ceto-enol, formando el binol exotérmicamente.
Área de la Ciencia:
- Química organometálica Química orgánica de los metales.
- La espectroscopia es una técnica de espectroscopia.
- Química computacional es la química computacional.
Sus antecedentes:
- Las reacciones de acoplamiento catalizadas por el cobre son vitales en la síntesis orgánica.
- La comprensión de los mecanismos de reacción a nivel molecular es crucial para el diseño de catalizadores.
- Los estudios de la fase gaseosa ofrecen una visión única de las vías de reacción, libres de los efectos del disolvente.
Objetivo del estudio:
- Para dilucidar el mecanismo de reacción del acoplamiento de naftol mediado por cobre.
- Para investigar el papel de TMEDA (N,N,N,N',N'-tetrametiletilendiamina) en el proceso de acoplamiento.
- Para caracterizar las especies intermedias involucradas en la fase gaseosa.
Principales métodos:
- Se empleó la espectroscopia de disociación multifotónica por infrarrojos (IRMPD, por sus siglas en inglés) para estudiar cúmulos binucleares aislados.
- Los cálculos de la Teoría Funcional de Densidad (DFT) se utilizaron para modelar la vía de reacción y la energía.
- Se logró el aislamiento de la fase gaseosa y la caracterización de los intermedios de reacción.
Principales resultados:
- La reacción de acoplamiento se lleva a cabo a través de grupos binucleares formados ad hoc: [{1-H}{2}{Cu}{2}{Cl}{TMEDA}{2}{+}{).
- Los espectros de IRMPD confirmaron la presencia de subunidades no acopladas de naftalatos dentro del grupo.
- Se identificó la irradiación como el desencadenante de la reacción de acoplamiento C-C.
- La tautomerización keto-enol del producto inicial impulsa el acoplamiento C-C, con la formación de binol siendo exotérmica (-0,61 eV).
- Se encontró que los acoplamientos análogos de C-O y O-O eran endotérmicos.
Conclusiones:
- El estudio revela un auténtico mecanismo de acoplamiento de naftol mediado por cobre en la fase gaseosa.
- Los grupos de cobre binucleares y la posterior irradiación son clave para iniciar la formación de enlaces C-C.
- La favorabilidad termodinámica de la tautomerización ceto-enol dicta la vía de acoplamiento C-C sobre los acoplamientos C-O u O-O.
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