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Ciclizaciones de eninas catalizadas por PtCl2 u otros cloruros de metales de transición: vías de reacción divergentes
M Méndez1, M P Muñoz, C Nevado
1Departamento de Química Orgánica, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain.
Journal of the American Chemical Society
|October 25, 2001
Resumen
El cloruro de platino ((II) cataliza la reacción de 1-en-6-ynes con alcoholes o agua, formando carbociclos con cadenas laterales funcionalizadas. Este proceso estereoselectivo implica la adición trans a través del doble enlace enyne, dando como resultado anillos de cinco o seis miembros.
Área de la Ciencia:
- Química organometálica Química orgánica de los metales.
- Síntesis orgánica La síntesis orgánica.
- La catálisis por catálisis.
Sus antecedentes:
- 1-en-6-ynes son sustratos versátiles en la síntesis orgánica.
- Las reacciones de ciclización catalizadas por metales ofrecen rutas eficientes a los compuestos cíclicos.
- Comprender los mecanismos de reacción es crucial para desarrollar nuevas metodologías sintéticas.
Objetivo del estudio:
- Para investigar la actividad catalítica de PtCl2 en la funcionalización de 1-en-6-ynes.
- Para explorar la estereoselectividad y el alcance de las reacciones de alkoxi- e hidroxiciclado.
- Para dilucidar el mecanismo de reacción utilizando métodos computacionales.
Principales métodos:
- Reacción de 1-en-6-ynes con alcoholes o agua utilizando el catalizador PtCl2.
- Investigación de catalizadores alternativos como los cloruros de Ru (II) y Au (III).
- Cálculos de la Teoría Funcional de Densidad (DFT) para identificar los principales intermediarios y vías de reacción.
Principales resultados:
- PtCl2 cataliza eficientemente la formación de carbociclos con grupos alcoxi o hidroxi de 1-en-6-ynes.
- La reacción procede a través de la adición estereoselectiva de trans al doble enlace de enyne.
- Los cálculos de DFT identificaron un complejo de ciclopropilo platinacarbeno como un intermediario clave.
- PtCl2 también cataliza la cicloisomerización de 1-en-6-ynes en disolventes polares no nucleófilos a través de un intermediario de platinaciclopenteno.
- Los cloruros de Ru (II) y Au (III) muestran una actividad limitada para la alcoxi- o hidrociclización.
- Los catalizadores Ru son efectivos para la cicloisomerización de las eninas con alquenos disubstituidos.
Conclusiones:
- PtCl2 es un catalizador eficaz para la síntesis estereoselectiva de carbociclos funcionalizados de 1-en-6-ynes.
- El mecanismo de reacción implica la activación del metal-alquino y el ataque nucleófilo estereoselectivo.
- Los cálculos de DFT proporcionan información valiosa sobre los intermediarios y vías de reacción.
- Se pueden emplear catalizadores metálicos alternativos y condiciones de reacción para las transformaciones relacionadas.
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