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Reducción de abedul organocatalizada impulsada por la luz visible
Justin P Cole1, Dian-Feng Chen1, Max Kudisch1
1Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, United States.
Journal of the American Chemical Society
|July 15, 2020
Resumen
Los nuevos catalizadores orgánicos de fotorreducción permiten las reducciones de abedul sin metales de arenas como el benceno utilizando luz visible. Este avance ofrece un método sostenible para sintetizar valiosos 1,4-ciclohexadienos a temperatura ambiente.
Área de la Ciencia:
- Química orgánica
- Fotocatálisis
- Metodología sintética
Sus antecedentes:
- La reducción de Birch es un método clave para convertir compuestos aromáticos en 1,4-ciclohexadienos utilizando electrones solvados.
- Las reducciones tradicionales de abedul requieren condiciones duras, generalmente involucrando metales alcalinos en amoníaco, limitando su aplicación con arenas no activadas como el benceno.
- Los catalizadores fotorredóxicos existentes carecen del potencial de reducción necesario para realizar las reducciones de Birch en sustratos difíciles como el benceno.
Objetivo del estudio:
- Desarrollar nuevos catalizadores orgánicos de fotorreducción capaces de llevar a cabo reducciones de Birch en condiciones de luz visible suave.
- Demostrar la eficacia de estos catalizadores en la reducción de arenos no activados, incluido el benceno.
- Establecer una alternativa sostenible y libre de metales a los protocolos tradicionales de reducción de abedul.
Principales métodos:
- Introducción de las imidas de benzo[ghi]perileno como catalizadores orgánicos de fotorreducción.
- Irradiación de luz visible utilizando LEDs disponibles en el mercado para impulsar las reacciones de reducción.
- Condiciones de reacción sin metales a temperatura ambiente.
- Estudios mecánicos para elucidar el ciclo catalítico y los procesos de transferencia de energía.
Principales resultados:
- El benceno y otros arenos funcionalizados se convirtieron con éxito en 1,4-ciclohexadienos en rendimientos moderados a buenos.
- Las reacciones procedieron eficientemente utilizando cargas de catalizador bajas (<1 mol por ciento).
- El proceso era completamente libre de metales y se operaba a temperatura ambiente y con luz visible.
- Las investigaciones mecanicistas revelaron un mecanismo de recolección de energía de dos fotones por el catalizador fotorredóxido orgánico.
Conclusiones:
- Las imidas de benzo[ghi]perileno funcionan como catalizadores orgánicos de fotorreducción para las reducciones de Birch.
- Esta metodología permite la síntesis sin metales de 1,4-ciclohexadienos a partir de arenas a temperatura ambiente, impulsada por la luz visible.
- El sistema catalítico desarrollado supera las limitaciones de las reducciones Birch tradicionales y los catalizadores fotorredóxicos existentes para reducir el benceno.
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