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Síntesis eficiente de ciclopropanos huérfanos utilizando sulfonas como equivalentes de carbeno

John Douglas Johnson¹, Charles Reece Teeples¹, Nicholas Rajai Akkawi¹

¹Department of Chemistry, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States.

Journal of the American Chemical Society

|August 8, 2022

Resumen

Este estudio introduce un nuevo método para sintetizar los 1,1-dialciclopropanos, productos naturales cruciales, utilizando aniones sulfonilo. Este enfoque supera las limitaciones de la transferencia de carbenos catalizados por metales, lo que permite una formación eficiente de ciclopropano.

Área de la Ciencia:

Química orgánica
Química sintética
Catálisis

Sus antecedentes:

Los 1,1-dialciclopropanos son motivos estructurales importantes que se encuentran en numerosos productos naturales.
Los métodos sintéticos existentes, como la transferencia de carbenos catalizados por metales, a menudo sufren reacciones secundarias competidoras como los desplazamientos de 1,2-hidruro, lo que limita su eficiencia y alcance.

Objetivo del estudio:

Desarrollar un método nuevo y mecánicamente distinto para la síntesis de 1,1-dialciclopropanos.
Proporcionar una alternativa a los métodos actuales que evite las reacciones secundarias problemáticas.

Principales métodos:

Utilizando reacciones de carbometalación de aniones dialquil sulfonilo con las olefinas.
Utilizando amida de sodio (NaNH2) o n-butilitio (n-BuLi) como bases en disolventes etéreos.
Reaccionan los dialquilosulfonos con los estirenos y los arilbutadienos a temperaturas comprendidas entre 23 y 70 °C.

Principales resultados:

Se han sintetizado con éxito varios 1,1-dialciclopropanos con altos rendimientos aislados (hasta el 89%).
Demostró la versatilidad del método con 16 estirenos diferentes, 9 arilbutadienos y 13 sulfonas diferentes.
Informó un ejemplo de una reacción de ciclopropanación secuencial, mostrando el potencial del método para la síntesis compleja.
Los estudios mecanicistas preliminares indicaron un proceso aniónico gradual iniciado por la adición de anión sulfonilo.

Conclusiones:

El método desarrollado proporciona una plataforma eficiente y versátil para sintetizar 1,1-dialciclopropanos.
Este enfoque de carbometalización ofrece una valiosa alternativa a las estrategias sintéticas existentes, superando las limitaciones asociadas con la transferencia de carbenos catalizados por metales.
La reacción procede a través de una vía aniónica distinta, expandiendo el conjunto de herramientas para la síntesis de ciclopropano.

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