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Catalizador de transferencia de fase dianiónico para fluorociclado asimétrico

Hiromichi Egami1, Tomoki Niwa1, Hitomi Sato1

  • 1School of Pharmaceutical Sciences, University of Shizuoka , 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan.

Journal of the American Chemical Society
|February 10, 2018
PubMed
Resumen
Este resumen es generado por máquina.

Los investigadores desarrollaron nuevos precatalizadores de ácido dicarboxílico para la fluoración asimétrica. Estos catalizadores permiten una síntesis enantioselectiva eficiente de dihidroxazinas fluoradas a partir de amidas alilicas a través de una novedosa ciclización 6-endofluoro.

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Área de la Ciencia:

  • Química orgánica
  • Catálisis asimétrica
  • Química de la fluoración

Sus antecedentes:

  • Los reactivos fluorados electrófilos como el Selectfluor son cruciales en la síntesis orgánica.
  • El desarrollo de métodos catalíticos eficientes y selectivos para la introducción de flúor es un desafío importante.
  • La catálisis de transferencia de fase ofrece una plataforma versátil para diversas transformaciones orgánicas.

Objetivo del estudio:

  • Diseñar y sintetizar nuevos precatalizadores de ácido dicarboxílico para la fluoración asimétrica.
  • Investigar la actividad catalítica de estos precatalizadores en la fluoración enantioselectiva de alquenos.
  • Explorar el alcance y las limitaciones del sistema catalítico desarrollado.

Principales métodos:

  • Diseño racional de los precatalizadores de ácido dicarboxílico inspirado en la estructura de Selectfluor.
  • Desprotonación de los precatalizadores para generar catalizadores de transferencia aniónica.
  • Reacciones de fluoración asimétricas que utilizan amidas alilicas y alceno acíclicos como sustratos.
  • Análisis de la enantioselectividad y la diastereoselectividad mediante cromatografía quiral y espectroscopia de RMN.

Principales resultados:

  • Se sintetizó y evaluó una serie de precatalizadores de ácido dicarboxílico.
  • El precatalizador 2a demostró una alta eficiencia en la catalización de la 6-endo-fluorociclización de las amidas alilicas.
  • Se obtuvieron productos fluorados de dihidroxazina con una excelente enantioselectividad (hasta el 99% ee).
  • Los alquenos trisubstituidos acíclicos reaccionaron con buena diastereoselectividad, mientras que los alquenos disubstituidos lineales mostraron una selectividad más baja.

Conclusiones:

  • Los precatalizadores de ácido dicarboxílico desarrollados funcionan eficazmente como catalizadores de transferencia de fase aniónica para la fluoración asimétrica.
  • La 6-endo-fluoro-ciclización representa una transformación sin precedentes para la síntesis de dihidroxazinas fluoradas.
  • Es probable que el mecanismo de reacción implique un intermediario fluorocarbocativo, lo que proporciona información para un mayor desarrollo del catalizador.