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Preparation of Stable Bicyclic Aziridinium Ions and Their Ring-Opening for the Synthesis of Azaheterocycles
Published on: August 22, 2018
Investigación experimental sobre el mecanismo de la quelación asistida, el cobre (II) acelerado con acetato
Gui-Chao Kuang1, Pampa M Guha, Wendy S Brotherton
1Department of Chemistry and Biochemistry, Florida State University, Tallahassee, 32306-4390, United States.
Journal of the American Chemical Society
|August 4, 2011
Resumen
Este estudio revela cómo las azidas quelantes y el acetato de cobre aceleran las reacciones de cicloadición azida-alquina. Un modelo mecanicista pone de relieve el papel crucial de las interacciones cobre ((I/II) /azida y las especies de cobre dinuclear de valencia mixta en la catálisis.
Área de la Ciencia:
- Química orgánica es la química orgánica.
- La catálisis de la catálisis.
- Mecanismos de reacción Mecanismos de reacción
Sus antecedentes:
- La cicloadición azida-alquina catalizada por el cobre (AAC) es una reacción de "clic química" vital.
- La alta reactividad de las azidas quelantes con el acetato de cobre (CuOAc) en las reacciones AAC requiere una explicación mecánica.
Objetivo del estudio:
- Formular un modelo mecanicista para las reacciones AAC mediadas por cobre acelerado (II) que involucran azidas quelatantes.
- Para dilucidar las funciones de los iones de cobre en diferentes estados de oxidación y la influencia del disolvente en la vía de reacción.
Principales métodos:
- Desarrollo de ensayos de fluorescencia y (1) H RMN para el monitoreo de la reacción.
- Estudios cinéticos que incluyen el efecto isotópico cinético del disolvente y experimentos de premezcla.
- Análisis de la estructura cristalina de rayos X de azidas quelantes con Cu(OAc) ((2).
Principales resultados:
- Se identificaron distintas reacciones de inducción para la conversión del cobre (II) a cobre (I) en metanol (oxidación del metanol) y acetonitrilo (homoacoplamiento oxidativo alquino).
- Órdenes cinéticos determinados, que revelan una rápida interacción de pre-equilibrio entre los iones de cobre y las azidas quelantes.
- Se observó una sinergia mecánica entre el homoacoplamiento oxidativo alquino y el AAC, que involucra vías bimetálicas y catálisis de bases.
Conclusiones:
- Se propone una especie de cobre dinuclear de valencia mixta (+2 y +1) como un catalizador altamente eficiente debido a las distintas funciones de los dos centros de cobre.
- Hizo hincapié en la importancia cinética de las interacciones cobre (I/II) /azida, complementando el enfoque existente en las interacciones cobre (I) /alquina.
- Proporcionó una base mecanicista para las reacciones rápidas de AAC mediadas por Cu(OAc)(2) con azidas quelantes, con implicaciones prácticas para la catálisis.
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