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Las vías de reacción que conducen a los macrociclos de etileno-arileno a través de la metátesis de alquina

Wei Zhang¹, Jeffrey S Moore

¹Roger Adams Laboratory, Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.

Journal of the American Chemical Society

|August 18, 2005

Resumen

Este estudio revela que la metátesis de alquino catalizado por molibdeno forma macrociclos de etileno y etileno. La formación del macrociclo está controlada termodinámicamente, siendo el hexámero cíclico el producto más estable, pero los subproductos de dialquilalquina pueden inhibir el catalizador.

Área de la Ciencia:

Química orgánica es la química orgánica.
La catálisis es la catálisis.
Ciencias Macromoleculares Ciencias Macromoleculares

Sus antecedentes:

La metátesis alquina es una herramienta poderosa para la formación de enlaces carbono-carbono.
La síntesis directa de los macrociclos de etileno-arileno sigue siendo un desafío.
Los catalizadores de molibdeno ofrecen una reactividad única para las transformaciones de alquinos.

Objetivo del estudio:

Investigar el mecanismo de la formación directa del macrociclo del arileno etileno a través de la metátesis del alquino.
Aclarar los factores que controlan el tamaño y la estabilidad del macrociclo.
Para identificar posibles vías de inhibición del catalizador.

Principales métodos:

Reacciones de metátesis de alquino utilizando un catalizador de molibdeno.
Análisis del producto mediante cromatografía por permeación de gel (GPC) y espectrometría de masas MALDI.
Temperatura variable y experimentos de mezclado para evaluar la reversibilidad de la reacción.

Principales resultados:

Formación inicial de oligómeros lineales y grandes macrociclos, seguido de la equilibración al hexámero cíclico más estable.
La formación del macrociclo está controlada termodinámicamente, no cinéticamente.
El subproducto 3-hexina inhibe el catalizador de molibdeno, en particular para sustratos de arilo.

Conclusiones:

La estabilidad termodinámica dicta la distribución final del macrociclo en la metátesis de alquino catalizado por molibdeno.
Los subproductos de la dialquilalquina pueden atrapar el catalizador, lo que dificulta la metástasis productiva de las arylalquinas.
Evitar o eliminar los subproductos de alquina sustituidos por dialquilo es crucial para la síntesis eficiente de macrociclos que contienen arilo.

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