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Los radicales como grupos excepcionales que retiran electrones: Sustitución aromática nucleofílica de los halofenolos
Nick Y Shin1, Elaine Tsui1, Adam Reinhold1
1Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States.
Journal of the American Chemical Society
|November 17, 2022
Resumen
Este estudio introduce un nuevo método que utiliza radicales fenoxilo para activar halofenoles para la sustitución aromática nucleofílica. Esta estrategia basada en radicales facilita las reacciones de acoplamiento desafiantes en condiciones suaves.
Área de la Ciencia:
- Química orgánica
- Química Física
- Mecanismos de reacción
Sus antecedentes:
- Los radicales centrados en heteroátomos son conocidos como electrófilos.
- El uso de radicales como grupos transitorios de retirada de electrones para reacciones polares remotas está subdesarrollado.
Objetivo del estudio:
- Desarrollar una nueva estrategia para la activación electrónica de halofenoles utilizando radicales.
- Para permitir la sustitución aromática nucleofílica directa de haluros por carboxilatos.
Principales métodos:
- Generación de radicales fenoxilo a través de la homólisis del enlace arilo O-H.
- Radiólisis de pulso y espectroscopia de absorción transitoria.
- Estudios mecánicos y computacionales.
Principales resultados:
- El radical fenoxilo actúa como un potente grupo de retiro de electrones (σp - O •) = 2,79).
- Sustitución aromática nucleofílica de haluros con carboxilatos obtenida bajo condiciones suaves.
- Barrera de reacción reducida en >20 kcal/mol en comparación con los fenoles de cáscara cerrada.
Conclusiones:
- Los radicales pueden servir como grupos activadores transitorios para las transformaciones químicas.
- La activación electrónica habilitada para la homólisis amplía el alcance de los acoplamientos nucleófilo-electrófilo.
- Esta estrategia permite reacciones químicas que antes eran difíciles.
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