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Fotociclado anaeróbico altamente regioselectivo de las 3-estirilpiridinas
F D Lewis1, R S Kalgutkar, J S Yang
1Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, USA. lewis@chem.northwestern.edu
Journal of the American Chemical Society
|July 18, 2001
Resumen
Las reacciones fotoquímicas de las estirilpiridinas y las aminostirilpiridinas producen azaphenantrenos. Bajo condiciones anaerobias, los derivados de 3-estirilpiridina forman selectivamente 2-azafenantrenos a través de un intermediario estable de dihidropiridina.
Área de la Ciencia:
- Fotoquímica orgánica y fotoquímica orgánica.
- Química Heterocíclica La Química Heterocíclica es una de las más conocidas.
- Mecanismos de reacción Mecanismos de reacción
Sus antecedentes:
- Las estirilpiridinas y las aminostirilpiridinas son importantes compuestos heterocíclicos.
- Comprender sus transformaciones fotoquímicas es crucial para las aplicaciones sintéticas.
Objetivo del estudio:
- Para investigar el comportamiento fotoquímico de las cis-estirilpiridinas y las aminostirilpiridinas.
- Para dilucidar los mecanismos de reacción y la regioselectividad de la formación de azaphenanthrene.
Principales métodos:
- Irradiación fotoquímica en condiciones aeróbicas y anaeróbicas.
- Caracterización espectroscópica (1H RMN, absorción electrónica) de los productos intermedios.
- Comparación de espectros experimentales y calculados.
Principales resultados:
- Formación regioselectiva de 2-azafenantrenos a partir de 3-estirilpiridina y su derivado 3'-amino bajo condiciones anaerobias.
- Formación de productos mixtos de 2- y 4-azafenantreno en presencia de oxígeno.
- Identificación de un intermediario de 1,4-dihidropiridina moderadamente estable formado a través de un desplazamiento de 1,7-hidrógeno.
Conclusiones:
- La regioselectividad de la fotociclización está influenciada por las tasas de apertura del anillo, los reordenamientos sigmatrópicos y el apagado del oxígeno.
- Un mecanismo propuesto implica un cambio de 1,7-hidrógeno que conduce a un intermediario de dihidropiridina, que posteriormente forma el producto azaphenanthrene.
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