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Control de la quimioselectividad en la activación de enlaces C-X vinílico y alilico con catálisis de paladio: un
Michael G Organ1, Elena A Arvanitis, Craig E Dixon
1Contribution from the Department of Chemistry, York University, 4700 Keele Street, Toronto, Ontario, Canada M3J 1P3.
Journal of the American Chemical Society
|February 14, 2002
Resumen
Un solo catalizador de paladio permite la sustitución selectiva de alelo o vinilo en olefinas polifuncionalizadas mediante el ajuste de la acidez del grupo saliente. Esto ofrece secuencias sintéticas intercambiables para la construcción de moléculas complejas.
Área de la Ciencia:
- Química orgánica es la química orgánica.
- La catálisis de la catálisis.
- Metodología sintética de la metodología sintética.
Sus antecedentes:
- Las reacciones catalizadas por el paladio son cruciales en la síntesis orgánica.
- El control de la selectividad en sustratos polifuncionalizados sigue siendo un desafío.
- Los distintos mecanismos de reacción a menudo requieren diferentes sistemas catalíticos.
Objetivo del estudio:
- Demostrar el uso intercambiable de un solo catalizador de paladio para distintas vías de reacción.
- Explorar la sustitución alelica selectiva y el acoplamiento cruzado vinílico en los bloques de construcción de las olefinas.
- Investigar la influencia de la acidez del grupo saliente en la selectividad de la reacción.
Principales métodos:
- Utilizando un catalizador de paladio con bloques de construcción de olefinas polifuncionalizadas.
- Modulación de la pK (a) del ácido conjugado del grupo alelico saliente.
- Empleando nucleófilos y componentes de reacción de Suzuki.
- Reacción secuencial que se desencadena mediante el calentamiento.
Principales resultados:
- Se logró la sustitución alelica selectiva en el 2,3-dibromo-1-propeno utilizando un nucleófilo malonato, incluso con los reactivos de acoplamiento de Suzuki presentes.
- Se realizó un acoplamiento cruzado vinílico selectivo en 2-bromo-1-(4-etilfenoxi)-2-propeno sin activar el grupo alelico.
- El mismo catalizador de paladio facilitó ambas reacciones secuenciales, con el calentamiento promoviendo el segundo paso.
Conclusiones:
- Un solo catalizador de paladio puede ser dirigido selectivamente hacia la sustitución de alelo o vinilo acoplamiento cruzado sintonizando las propiedades electrónicas del grupo de salida.
- Este enfoque permite reacciones catalíticas intercambiables y secuenciales en sustratos complejos de olefinas.
- Los hallazgos ofrecen una estrategia versátil para construir moléculas polifuncionalizadas.
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