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N-heterocíclicos carbenos catalizados por adiciones conjugadas de alcoholes

Eric M Phillips¹, Matthias Riedrich, Karl A Scheidt

¹Department of Chemistry, Center for Molecular Innovation and Drug Discovery, Chemistry of Life Processes Institute, Northwestern University, Silverman Hall, 2145 Sheridan Road, Evanston, Illinois 60208, USA.

Journal of the American Chemical Society

|September 3, 2010

Resumen

Los carbenos N-heterocíclicos catalizan eficientemente la adición de alcoholes a los alquenos y ynones activados, formando éteres de vinilo y permitiendo reacciones en tándem sin oligomerización. Esta hidroalcoxilación ofrece una vía sintética suave y eficaz.

Área de la Ciencia:

Química orgánica es la química orgánica.
La catálisis es la catálisis.
Metodología sintética de la metodología sintética.

Sus antecedentes:

Los carbenos N-heterocíclicos (NHC, por sus siglas en inglés) son organocatalizadores versátiles.
Las reacciones de adición conjugada son cruciales para la formación de enlaces C-C y C-heteroatomo.
La hidroalcoxilación de alquenos e ynones sigue siendo un área para el desarrollo de sistemas catalíticos eficientes.

Objetivo del estudio:

Desarrollar una eficiente adición conjugada intermolecular de alcoholes a alquenos activados catalizados por NHCs.
Para explorar el alcance de los sustratos y nucleófilos para esta reacción.
Para investigar las reacciones catalizadas por NHC con ynones y procesos en tándem.

Principales métodos:

Utilizado el carbeno N-heterocíclico libre derivado de IMes·HCl como catalizador (5 mol %).
Se emplean alquenos activados (cetonas, ésteres) y varios alcoholes primarios/secundarios.
Reacciones investigadas con ynones y adición conjugada en tándem/Reacciones en cascada de Michael.

Principales resultados:

Se logra una adición conjugada intermolecular eficiente de alcoholes a los alquenos activados.
Demostró la utilidad de los alcoholes primarios y secundarios como nucleófilos.
No se observó ninguna oligomerización bajo condiciones suaves para una hidroalcoxilación efectiva.
Catalizó la formación de éteres vinílicos a partir de ynones y promovió reacciones en tándem.

Conclusiones:

Desarrolló una nueva hidroalcoxilación catalizada por NHC de alquenos activados.
Se estableció la eficacia del carbeno derivado de IMes·HCl para la adición de conjugados y la síntesis de éter vinílico.
Los estudios mecanicistas preliminares sugieren una vía de base de Brønsted para los carbenos libres.

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