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Dos mecanismos inusuales y competitivos para la ciclización del (2-etinilefenil) triazeno: reactividad
David B Kimball1, Rainer Herges, Michael M Haley
1Department of Chemistry, University of Oregon, Eugene, Oregon 97403-1253, USA.
Journal of the American Chemical Society
|February 21, 2002
Resumen
La ciclización a alta temperatura de (2-etinilefenil) triazenos produce cinolinas, mientras que la catálisis del cobre a temperaturas más bajas forma exclusivamente isoindazoles, revelando distintas vías de reacción.
Área de la Ciencia:
- Química orgánica es la química orgánica.
- Química Heterocíclica La Química Heterocíclica es una de las más conocidas.
Sus antecedentes:
- Los triazenos son precursores versátiles en la síntesis orgánica.
- El control de la vía de ciclización de los triazenos funcionalizados es crucial para acceder a diversos andamios heterocíclicos.
Objetivo del estudio:
- Para investigar las vías de reacción de (2-etinilefenil) triazenos bajo diferentes condiciones.
- Para dilucidar los mecanismos que conducen a la cinolina y la formación de isoindazol.
Principales métodos:
- Ciclización térmica en el ODCB.
- Cíclicación catalizada por cloruro de cobre en el 1,2-dicloroetano.
- Cálculos de la Teoría Funcional de la Densidad (DFT).
- Estudios de etiquetado de deuterio.
Principales resultados:
- Formación exclusiva de las cinolinas a través de la ciclización térmica a 200°C.
- Formación exclusiva de isoindazoles a través de la catálisis de CuCl a 50°C.
- Identificación de un intermediario de iones 3-dehidrocinnolinium en el ciclo térmico.
- Hay pruebas sólidas de un intermediario de carbeno en la formación de isoindazol.
Conclusiones:
- Las condiciones de reacción dictan el resultado de ciclización de (2-etinilefenil) triazenos.
- Mecanismos distintos, que involucran estados de transición pericíclicos y pseudocoarctatos, conducen a las cinolinas y los isoindazoles, respectivamente.
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