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La cara de Janus del ligando X en la cicloadición azida-alquina catalizada por el cobre

Liqun Jin¹, Erik A Romero¹, Mohand Melaimi¹

¹UCSD-CNRS Joint Research Laboratory (UMI 3555), Department of Chemistry and Biochemistry, University of California, San Diego , La Jolla, California 92093-0358, United States.

Journal of the American Chemical Society

|November 28, 2015

Resumen

El anión (X) en la cicloadición azida-alquina catalizada por cobre (CuAAC) tiene un impacto significativo en la cinética de la reacción. Los ligandos de acetato ofrecen un equilibrio, optimizando los pasos clave para una catálisis eficiente.

Área de la Ciencia:

Catálisis
Química orgánica
Mecanismos de reacción

Sus antecedentes:

La cicloadición azida-alquina catalizada por cobre (CuAAC) es una reacción crucial en varios campos químicos.
Comprender el papel de los ligandos y los contrarios es vital para optimizar la eficiencia de CuAAC.

Objetivo del estudio:

Para aclarar el efecto del anión (X) en la cinética de las etapas individuales en el ciclo catalítico CuAAC.
Identificar las combinaciones óptimas de ligando y anión para mejorar el rendimiento catalítico.

Principales métodos:

Se realizaron reacciones estequiométricas utilizando complejos de cobre con ligandos cíclicos (alquilo) y aminocarbenos (CAAC) y varios aniones (OTf, Cl, OAc, OPh, OtBu).
Se analizaron los perfiles cinéticos de las etapas del ciclo catalítico.

Principales resultados:

Los ligandos básicos aceleran la metalización pero impiden la formación de acetílidos bis (de cobre).
Los ligandos no nucleófilos favorecen la formación de acetílidos bis (de cobre) pero la metalización es lenta.
El acetato (OAc) demostró un equilibrio favorable entre la metalización y la formación de acetílidos de cobre.
El acetato demostró ser muy eficiente en el paso de proto-demetalización.

Conclusiones:

La elección del anión en CuAAC influye significativamente en las velocidades de las etapas catalíticas clave.
Los complejos cíclicos (alquilo) (amino) carbeno (CAAC) de cobre con aniones de acetato representan un sistema prometedor para las reacciones CuAAC eficientes.

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