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Ciclificación asimetrica catalizada por el rodio (III) de 1,6-dienos que contienen ciclohexadienona: un estudio
Yun-Xuan Tan1, Fang Zhang2, Pei-Pei Xie3
1CAS Key Laboratory of Synthetic Chemistry of Natural Substances, Center for Excellence in Molecular Synthesis , Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences , 345 Lingling Road , Shanghai 200032 , China.
Journal of the American Chemical Society
|July 27, 2019
Resumen
Este estudio introduce la primera ciclización borilativa asimétrica catalizada por el rodio (III) de 1,6-dienos. El método produce eficientemente compuestos cis-bicíclicos ópticamente puros con múltiples estereocentros.
Área de la Ciencia:
- Química orgánica
- Catálisis
- Síntesis estereoselectiva
Sus antecedentes:
- La diferenciación de las olefinas en la ciclización asimétrica catalizada por metales de 1,6-dienos es intrínsecamente difícil.
- El desarrollo de métodos eficientes para sintetizar estructuras cíclicas complejas con múltiples estereocentros sigue siendo un desafío en la química orgánica.
Objetivo del estudio:
- Desarrollar la primera ciclización borilativa asimétrica catalizada por el rodio (III) de 1,6-dienos atados a ciclohexadienona.
- Para lograr altos rendimientos y estereoselectividades en la síntesis de esqueletos cis-bicíclicos ópticamente puros.
Principales métodos:
- Reacción de ciclización borilativa asimétrica catalizada por el rodio.
- Se utilizan alquenos (1,6-dienes) mono-, 1,1-di- y (E) -1,2-disubstituidos atados a ciclohexadienona.
- Se emplearon SAESI-MS (Espectrometría de masas de ionización por electrospray) y estudios computacionales para aclarar el ciclo catalítico.
Principales resultados:
- Con éxito sintetizó esqueletos ópticamente puros cis-bicíclicos con tres o cuatro estereocentros contiguos.
- Se obtienen altos rendimientos (25-93%) y excelentes diastereoselectividades (> 20:1 dr) y enantioselectividades (90-99% ee).
- Compatibilidad demostrada con una amplia gama de grupos funcionales, lo que permite una fácil conversión de productos.
Conclusiones:
- Se estableció una nueva ciclización borilativa asimétrica catalizada por rodio (III) de 1,6-dienos.
- Se propuso un ciclo catalítico Rh (I) / (III) que involucra pasos clave como la adición oxidativa, la inserción de olefinas, la adición conjugada y la eliminación reductiva.
- Destacó el papel de la deformación del anillo en el control de la regioselectividad y favoreció la formación de estructuras 5,6-bicíclicas, proporcionando una base para futuros diseños de reacción.
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