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El mecanismo de la migración de 1,4 grupos alquilo en ylidos de halonio hipervalentes: el curso estereoquímico

Robert M Moriarty¹, Sachin Tyagi, Daniela Ivanov

¹Department of Chemistry, University of Illinois at Chicago, 845 West Taylor Street, Chicago, Illinois 60607-7061, USA. moriarty@uic.edu

Journal of the American Chemical Society

|May 22, 2008

Resumen

El acetato de rodio ((II) cataliza la descomposición del yeloide, formando halociclohexenonas a través de una migración de 1,4-alquilo. Esta reacción procede con una alta retención estereoquímica y una baja energía de activación, ofreciendo una nueva vía sintética.

Área de la Ciencia:

Química orgánica es la química orgánica.
Química organometálica Química orgánica de los metales.
Mecanismos de reacción Mecanismos de reacción

Sus antecedentes:

Las reacciones catalizadas por metales son cruciales para la síntesis orgánica.
Los ylidos de yodo son versátiles intermediarios sintéticos.
Comprender los mecanismos de reacción ayuda en el desarrollo de nuevas metodologías sintéticas.

Objetivo del estudio:

Para investigar la descomposición catalizada por el acetato de rodio (II) del ciclohexanodión feniliodonio ylides.
Para dilucidar el mecanismo de la migración del grupo 1,4-alquilo en presencia de haluros de alquilo.
Para explorar la vía de reacción con haluros de alilo y de arilo.

Principales métodos:

Descomposición catalítica de los ylidos de yodo utilizando el acetato de rodio (II).
Reacción con varios haluros de alquilo, alilo y arilo.
Análisis estereoquímico utilizando sustratos quirales.
Cálculos teóricos (B3LYP/6-31G) para determinar la energía de activación.

Principales resultados:

Formación de 3-alcoxi-2-halociclohex-2-enonas a través de una migración intramolecular concertada de 1,4-alquilo.
Se observó una alta retención de la configuración (88,6%) con el cloruro de (S) -alfa-fenetil.
Se produjo una reorganización similar a la de Claisen con haluros alílicos.
Los haluros de arilo producían productos de sustitución aromática electrófila.

Conclusiones:

La reacción catalizada por el rodio proporciona una nueva ruta a las ciclohexenonas funcionalizadas.
El mecanismo implica una migración de un intermediario de halonio y de un grupo halógeno-oxígeno.
La vía de reacción es sensible a la naturaleza del haluro, ofreciendo diversos resultados sintéticos.

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