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Cavitandos como acompañantes para las reacciones monofuncionales y de formación de anillos en el agua
Nai-Wei Wu1, Julius Rebek1,2
1Department of Chemistry, Fudan University , 220 Handan Road, Shanghai 200433, China.
Journal of the American Chemical Society
|June 4, 2016
Resumen
Las cavitandas aceleran la formación de anillos medianos a grandes acercando los extremos reactivos en una solución acuosa. Este método supera las tensiones internas, aumentando las tasas de ciclización de los diisocianatos a las ureas cíclicas.
Área de la Ciencia:
- Química supramolecular
- Síntesis orgánica
Sus antecedentes:
- Las reacciones de ciclización que forman anillos de tamaño mediano a menudo son lentas debido a la tensión molecular interna.
- Las técnicas de alta dilución se utilizan para favorecer la ciclización intramolecular sobre las reacciones intermoleculares, pero no aceleran la ciclización en sí misma.
Objetivo del estudio:
- Investigar el uso de cavitandos como huéspedes moleculares para promover la formación de compuestos cíclicos de tamaño medio a grande.
- Mejorar las tasas de ciclización utilizando la complejación huésped-huésped en solución acuosa.
Principales métodos:
- Aplicación de cavitantes solubles en agua para facilitar la conversión de los diisocianatos de cadena larga en ureas cíclicas.
- Conducir reacciones en solución de óxido de deuterio (D2O) para aprovechar las fuerzas hidrofóbicas para la preorganización de moléculas invitadas.
- Utilizando las conformaciones pre-organizadas y dobladas dentro de los cavitandos para acercar los terminales reactivos.
Principales resultados:
- La complejación de Cavitand preorganiza efectivamente a los huéspedes diisocianados en conformaciones que reducen la tensión interna.
- La proximidad de los extremos reactivos dentro de la cavidad acelera significativamente las tasas de reacción de ciclización.
- Este enfoque supramolecular supera con éxito las barreras cinéticas asociadas con la formación de anillos de tamaño medio a grande.
Conclusiones:
- Los cavitandos solubles en agua son herramientas efectivas para acelerar reacciones de ciclización difíciles en medios acuosos.
- La estrategia de complejación huésped-huésped ofrece una ruta prometedora para sintetizar ureas cíclicas y potencialmente otros anillos de tamaño medio a grande.
- Esta metodología tiene implicaciones para las reacciones de funcionalización remota y otros procesos sintéticos que requieren un ensamblaje molecular controlado.
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