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La alfa-ariación catalizada por paladio de ésteres y amidas en condiciones más neutras
Takuo Hama1, Xiaoxiang Liu, Darcy A Culkin
1Department of Chemistry, Yale University, P.O. Box 208107, New Haven, Connecticut 06520-8107, USA.
Journal of the American Chemical Society
|October 14, 2005
Resumen
Nuevos métodos catalizados por paladio permiten la alfa-ariación de compuestos carbonílicos utilizando condiciones más suaves. Estas reacciones ofrecen altos rendimientos y tolerancia del grupo funcional para sintetizar ésteres y amidas valiosos.
Área de la Ciencia:
- Química orgánica es la química orgánica.
- La catálisis por catálisis.
- Metodología sintética de la metodología sintética.
Sus antecedentes:
- La alfa-arilación tradicional a menudo requiere condiciones duras incompatibles con los grupos funcionales sensibles.
- El desarrollo de condiciones más suaves y neutrales es crucial para aplicaciones sintéticas más amplias.
Objetivo del estudio:
- Informar de dos nuevos procedimientos para la alfa-arilación de compuestos carbonílicos en condiciones neutras.
- Demostrar altos rendimientos y tolerancia del grupo funcional en estas nuevas reacciones.
Principales métodos:
- Utilizando catalizadores de paladio con ligandos de fosfina obstaculizados (Q-phos) y complejos diméricos Pd(I).
- Empleando enolados de zinc derivados de ésteres/amidas de alfa-bromo que reaccionan con haluros de arilo.
- El segundo método consiste en que los acetales de silil ceteno/ketimina reaccionan con bromuros de arilo utilizando fluoruro de zinc y catalizadores de paladio.
Principales resultados:
- Los altos rendimientos de ésteres alfa-arilo y amidas se logran con una carga de catalizador de 1-2 mol%.
- Se ha demostrado una notable tolerancia del grupo funcional, incluidos los grupos sensibles a la base.
- Se ha reportado un acoplamiento diastereoselectivo exitoso sin racionalización de los estereocentros.
Conclusiones:
- Los procedimientos desarrollados ofrecen rutas eficientes y suaves para la alfa-arilación.
- Estos métodos amplían el alcance de las reacciones de acoplamiento cruzado catalizadas por paladio.
- Las condiciones neutras preservan los grupos funcionales sensibles y los estereocentros.
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