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La activación a través del espacio puede anular los efectos de sustitución en la sustitución aromática electrofílica

Liangyu Guan¹, Maxwell Gargiulo Holl¹, Cody Ross Pitts¹

¹Department of Chemistry, Johns Hopkins University , 3400 North Charles Street, Baltimore, Maryland 21218, United States.

Journal of the American Chemical Society

|October 11, 2017

Resumen

Los anillos aromáticos con deficiencia de electrones reaccionan inesperadamente más rápido que los ricos en electrones debido a una nueva interacción de enlace de hidrógeno. Esta activación de HO-areno supera la desactivación, lo que permite la sustitución preferente y una mayor reactividad en las reacciones de sustitución aromática electrófila (EAS).

Área de la Ciencia:

Química orgánica
Mecanismos de reacción

Sus antecedentes:

La sustitución aromática electrofílica (EAS) generalmente favorece los anillos aromáticos ricos en electrones.
Las arenas con deficiencia de electrones son generalmente menos reactivas hacia los electrófilos.

Objetivo del estudio:

Investigar patrones de reactividad inusuales en la sustitución aromática electrofílica.
Explorar el papel de las interacciones de enlace de hidrógeno en la dirección de las reacciones EAS.
Demostrar la sustitución preferencial en las arenas con déficit de electrones.

Principales métodos:

Experimentos de competencia intramolecular que involucran arenas ricas en electrones y deficientes en electrones.
Aprovechamiento de una interacción de OH-areno con enlace de hidrógeno con HO-areno para la activación.
Demostración de la activación del HO-areno superando grupos desactivadores fuertes como los sustituyentes del trifluorometil.

Principales resultados:

Las arenas con déficit de electrones exhibieron una sustitución preferencial sobre las arenas ricas en electrones.
La activación de HO-areno superó con éxito el efecto desactivador de un grupo trifluorometil.
La activación mejorada de HO-areno promovió la tetrabrominación de arenos con deficiencia de electrones.

Conclusiones:

Una nueva interacción de enlace de hidrógeno HO-areno puede activar arenas con déficit de electrones para EAS.
Este mecanismo de activación invierte las tendencias típicas de reactividad en EAS.
Los hallazgos ofrecen nuevas estrategias para la sustitución electrofílica y pueden informar sobre las interacciones biológicas.

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