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Reacciones de cicloadición de furanos dihapto-coordinados

Lee A Friedman¹, Michal Sabat, W Dean Harman

¹Department of Chemistry, University of Virginia, Charlottesville, Virginia 22901, USA.

Journal of the American Chemical Society

|June 20, 2002

Resumen

Los complejos de renio con ligandos de furano se someten a reacciones de cicloadición con TCNE y DMAD, formando nuevas estructuras de oxabiciclohepteno y oxabiciclo[3.2.0]heptadieno. Estas reacciones producen valiosos intermediarios para la síntesis de la oxepina.

Área de la Ciencia:

Química organometálica Química orgánica de los metales.
Síntesis orgánica La síntesis orgánica.
Coordinación Química de la Coordinación

Sus antecedentes:

Los complejos de renio con ligandos de hidridotris ((pyrazolyl) borato (Tp) son versátiles en las transformaciones organometálicas.
El furano y sus derivados sirven como sustratos clave en las reacciones de cicloadición.

Objetivo del estudio:

Para investigar la reactividad de cicloadición de los complejos [TpRe(CO)(L)(eta(2)-furano) ] con varios electrófilos.
Explorar la síntesis de nuevos derivados de oxabiciclohepteno y oxabiciclo[3.2.0]heptadieno.
Evaluar el potencial de estos productos como precursores para la síntesis de oxepina.

Principales métodos:

Síntesis de complejos de renio-furano con diferentes ligandos auxiliares (L).
Reacciones de cicloadición dipolar con tetracianoetileno (TCNE) y dimetil acetilenedicarboxilato (DMAD).
Caracterización estructural de productos, incluida la cristalografía de rayos X.
La descomplejación oxidativa y la conversión térmica en moléculas objetivo.

Principales resultados:

Las cicloadiciones dipolares con TCNE produjeron complejos de 7-oxabiciclohepteno.
Las reacciones con DMAD produjeron productos de cicloadición de ylide de carbonio y productos de cicloadición [2+2] con el enlace doble de furano.
Se observó la formación estereoselectiva de adutos [2+2] con furanos sustituidos.
La descomplejación oxidativa y el reordenamiento térmico proporcionaron a las oxepinas un buen rendimiento.

Conclusiones:

Los complejos de renio-furanos participan efectivamente en reacciones de cicloadición con alquenos y alquinas con déficit de electrones.
La vía de reacción (dipolar vs. [2+2] cicloadición) está influenciada por el electrófilo y el patrón de sustitución de furanos.
Los derivados sintetizados de oxabicicloheptadieno son valiosos precursores para la síntesis de la oxepina.

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