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Mecanismo de oxidación de alcohol aeróbico catalizado por cobre ((I) /TEMPO
Jessica M Hoover1, Bradford L Ryland, Shannon S Stahl
1Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706, USA.
Journal of the American Chemical Society
|January 16, 2013
Resumen
Este estudio investiga un sistema de catalizador de cobre / TEMPO para la oxidación del alcohol aeróbico. El mecanismo revela pasos de limitación de velocidad distintos para los alcoholes bencílicos frente a los alifáticos, ofreciendo información sobre el diseño del catalizador.
Área de la Ciencia:
- La catálisis de la catálisis.
- Química orgánica es la química orgánica.
- Reacciones de oxidación Reacciones de oxidación.
Sus antecedentes:
- Los catalizadores homogéneos de cobre/TEMPO (2,2,6,6-tetrametilpiperidina-N-oxilo) son efectivos para la oxidación del alcohol aeróbico.
- Un sistema (bpy) Cu(I) /TEMPO/NMI (N-metilimidazol) reportado previamente muestra altas tasas y selectividades, incluso para los alcoholes no activados.
Objetivo del estudio:
- Para llevar a cabo una investigación mecanicista del sistema catalizador (bpy) Cu(I) /TEMPO/NMI.
- Para comparar la reactividad y las vías mecanicistas de los alcoholes bencílicos y alifáticos.
Principales métodos:
- Análisis cinético mediante absorción de gases y espectroscopia de infrarrojos in situ.
- Caracterización de la especiación del catalizador mediante EPR y espectroscopia UV visible.
- Evaluación de los efectos cinéticos de los isótopos.
Principales resultados:
- Se aclaró un mecanismo catalítico de dos etapas: oxidación del catalizador por O2 y oxidación del sustrato.
- La oxidación del catalizador involucra un intermediario binuclear Cu(2) O(2).
- La oxidación del sustrato se produce a través del radical nitroxilo Cu (II) y TEMPO, que involucra un intermediario de Cu (II) -alcóxido.
Conclusiones:
- Las oxidaciones de alcohol bencílico y alifático exhiben diferentes pasos que limitan la rotación.
- La oxidación del catalizador por O2 es la velocidad limitante para los alcoholes bencílicos.
- Múltiples pasos contribuyen a la tasa de rotación para la oxidación del alcohol alifático.
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