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Intermedios superelectrófilos en la borilación aromática dirigida por nitrógeno

Timothy S De Vries¹, Aleksandrs Prokofjevs, Jeremy N Harvey

¹Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA.

Journal of the American Chemical Society

|October 15, 2009

Resumen

Este estudio introduce nuevas reacciones de borilación que forman iones cíclicos de borenio a partir de cationes de boro con puente de hidrógeno. Estas reacciones utilizan la abstracción de hidruro y demuestran vías de ciclización únicas, confirmadas por espectroscopia y análisis computacional.

Área de la Ciencia:

Química organometálica Química orgánica de los metales.
Síntesis orgánica La síntesis orgánica.
Química computacional es la química computacional.

Sus antecedentes:

Las reacciones de borilación son cruciales en la síntesis orgánica.
La generación y la reactividad de los iones de borenio son de gran interés.
La comprensión de los mecanismos de reacción que involucran cationes de boro es esencial para el desarrollo de nuevas metodologías sintéticas.

Objetivo del estudio:

Para describir los primeros ejemplos de borilación a través de cationes de boro con puente de hidrógeno.
Investigar la formación de iones cíclicos de borenio y derivados relacionados.
Para dilucidar el mecanismo de reacción utilizando enfoques experimentales y computacionales.

Principales métodos:

Abstracción de hidrógeno de los boranos N,N-dimetilamina mediante el uso de Ph ((3) C ((+) (C ((6) F ((5)) ((4) B ((-) (TrTPFPB).
Experimentos de apagado reductivo, espectroscopia de RMN (11) B y (1) H para la caracterización del producto.
Cálculos de la teoría funcional de densidad (DFT) (B3LYP/6-31G*) para evaluar los intermedios catiónicos y los estados de transición.

Principales resultados:

Generación exitosa de cationes con puente de hidrógeno y su posterior boroilación interna a derivados cíclicos de amina borano.
Se ha confirmado la formación de iones cíclicos de borenio para sustratos específicos (Ar = C6H5), n = 1 y Ar = o-C6H4) SiMe3).
Observación de un producto de ciclización único con un sustituto tert-butilo y un efecto de isótopo cinético significativo (k (((H) / k (((D) = 2.8) para un sustrato orto-deuterado.

Conclusiones:

El estudio demuestra una nueva ruta a la borilación a través de cationes de boro con puente de hidrógeno.
Los mecanismos de reacción implican la inserción de C-H o los intermediarios de Wheland, con vías influenciadas por los sustituyentes del sustrato.
Los datos computacionales y experimentales proporcionan información sobre la formación y la estabilidad de los iones de borenio y los productos de ciclización.

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