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Olefin-borano "complejos de van der Waals": intermediarios en las reacciones frustradas de adición de pares de Lewis
Xiaoxi Zhao1, Douglas W Stephan
1Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario, Canada M5S 3H6.
Journal of the American Chemical Society
|July 21, 2011
Resumen
Este estudio revela que los complejos borano-olefina se forman a través de las interacciones de van der Waals antes de las reacciones de adición. Estos intermediarios reaccionan fácilmente con las bases de fosfina para crear productos zwitteriónicos cíclicos.
Área de la Ciencia:
- Química organometálica Química orgánica de los metales.
- Química supramolecular de las moléculas.
Sus antecedentes:
- La química del par de Lewis frustrado (FLP) involucra ácidos y bases de Lewis que no se asocian fácilmente.
- Comprender la complicación previa a la reacción es crucial para controlar la reactividad del FLP.
Objetivo del estudio:
- Investigar las interacciones iniciales entre los boranos y las olefinas antes de las reacciones de adición de FLP.
- Caracterizar la naturaleza de los complejos borano-olefina formados bajo condiciones específicas.
Principales métodos:
- Se utilizó la espectroscopia de RMN HOESY a bajas temperaturas (-50 °C).
- Empleó modelado computacional para apoyar observaciones experimentales.
- Sintetizó un compuesto modelo con un borano ácido de Lewis atado y un grupo vinílico.
Principales resultados:
- Los datos experimentales confirmaron la proximidad espacial entre los grupos borilo y vinilo.
- Los estudios computacionales indicaron la formación de un complejo borano-olefina de van der Waals.
- Identificó estos complejos como intermediarios clave en reacciones de adición posteriores.
Conclusiones:
- Los complejos de borano-olefina van der Waals son intermediarios transitorios en la química de las FLP.
- Estos productos intermedios se someten a reacciones de adición fáciles con bases de fosfina.
- La formación de productos zwitteriónicos cíclicos es facilitada por estos eventos de pre-complejación.
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