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Más allá de la reorganización de Roger Brown: topomerización atómica de largo alcance en polienas conjugadas

John Mabry¹, Richard P Johnson

¹Department of Chemistry, University of New Hampshire, Durham, New Hampshire 03824, USA.

Journal of the American Chemical Society

|May 30, 2002

Resumen

Se observó por primera vez la topomerización de largo alcance del átomo de carbono en 1,3-butadiinas. La pirólisis de vacío de flash indujo el equilibrio de la etiqueta entre los átomos de carbono, revelando procesos de intercambio de átomos y apoyando un nuevo mecanismo de reordenamiento.

Área de la Ciencia:

Química orgánica es la química orgánica.
La Química Física es la química física.
Química computacional es la química computacional.

Sus antecedentes:

Los sistemas 1,3-Diyne son bloques de construcción fundamentales en la síntesis orgánica.
Comprender los mecanismos de reorganización del átomo de carbono es crucial para predecir la reactividad.
Estudios previos han explorado la mezcla limitada de carbono en sistemas relacionados.

Objetivo del estudio:

Para demostrar y caracterizar la topomerización de largo alcance del átomo de carbono en una 1,3-diene.
Para dilucidar el mecanismo de intercambio de átomos de carbono a través de métodos experimentales y computacionales.
Investigar el panorama energético de los potenciales intermediarios de reordenamiento.

Principales métodos:

Síntesis de un precursor del 1-fenil-4-p-tolyl-1,3-butadieno enriquecido con (13) C.
La pirólisis en vacío de flash (FVP) a temperaturas controladas (800-900 °C) y presiones (0,01 Torr).
Espectroscopia de Resonancia Magnética Nuclear (RMN) para el análisis de distribución de etiquetas (13) C.
Teoría Funcional de Densidad (DFT) y cálculos de la teoría de perturbaciones de Moller-Plesset.

Principales resultados:

Casi completo (13) C etiqueta de equilibrio entre C-1 y C-2 observado a 800 ° C.
Migración significativa de la etiqueta (13)C hacia C-3 y C-4 a 900 °C.
Pruebas experimentales tanto para los procesos de intercambio de átomos de carbono intrabond y interbond.
Soporte computacional para un mecanismo que involucra el reordenamiento de Brown, la formación de trialeno y los intermediarios de vinilideno.
El trialeno se identificó como un intermediario de bajo nivel con un carácter diradical significativo.

Conclusiones:

La topomerización de largo alcance del átomo de carbono se puede lograr en 1,3-diynes a través de la reorganización térmica.
El intercambio de átomos intraenlace exhibe una barrera de activación más baja que el intercambio interenlace.
El mecanismo propuesto que involucra a los intermediarios de trialeno y vinilideno describe con precisión la topomerización observada.
Los datos computacionales proporcionan información clave sobre la energía y la viabilidad de la vía de reacción propuesta.

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