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Chemoselective Preparation of 1-Iodoalkynes, 1,2-Diiodoalkenes, and 1,1,2-Triiodoalkenes Based on the Oxidative Iodination of Terminal Alkynes
Published on: September 12, 2018
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Alquilaciones enantioselectivas catalizadas por pentanidio y bisguanidinio utilizando sililamida como probasa de
Bo Teng1, Wenchao Chen1, Shen Dong1
1Division of Chemistry and Biological Chemistry, Nanyang Technological University , 21 Nanyang Link, Singapore 637371.
Journal of the American Chemical Society
|July 23, 2016
Resumen
Una nueva estrategia de probasa de Brønsted permite la generación de bases fuertes transitorias para la catálisis de transferencia de fase asimétrica. Este método logra una alquilación altamente enantioselectiva de sustratos sensibles, minimizando las reacciones secundarias.
Área de la Ciencia:
- Química orgánica
- Catálisis
Sus antecedentes:
- Las reacciones asimétricas de transferencia de fase a menudo enfrentan desafíos con la selección de bases, equilibrando la activación del sustrato con la minimización de las reacciones de fondo.
- Las bases fuertes como los alcóxidos pueden activar sustratos, pero conducen a reacciones secundarias inevitables, mientras que las bases más leves como los carbonatos tienen un alcance limitado.
Objetivo del estudio:
- Desarrollar una nueva estrategia de prueba de Brønsted para generar una base sólida transitoria in situ.
- Para permitir una alquilación de transferencia de fase altamente enantioselectiva, especialmente para sustratos frágiles.
Principales métodos:
- Una estrategia de probasa de Brønsted que utiliza sililamida activada por fluoruro para generar una base fuerte transitoria in situ.
- Utilizando catalizadores de pentanidinio y bisguanidinio para la alquilación asimétrica de transferencia de fase.
- Investigando el papel de la probasa como un reactivo de silación.
Principales resultados:
- Alquilación de transferencia de fase altamente enantioselectiva de varios sustratos, incluida la dihidrocumarina (lactona).
- Se ha demostrado que la probasa actúa como un reactivo de silación, formando los principales éteres sililenoles o los intermedios sililcetenoacetales.
- Propuso la formación de pares de iones de silicato-fluoruro hipervalentes con catalizadores como intermedios cruciales.
Conclusiones:
- La estrategia de probasa de Brønsted genera efectivamente bases fuertes transitorias, reduciendo las reacciones secundarias en la catálisis de transferencia de fase asimétrica.
- Este enfoque amplía el alcance de los sustratos susceptibles a la alquilación enantioselectiva.
- El mecanismo propuesto que involucra productos intermedios de silicato hipervalentes proporciona información sobre el control estereoquímico observado.
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