Video Experimental Relacionado

Updated: May 4, 2026

Isolating Free Carbenes, their Mixed Dimers and Organic Radicals

Isolating Free Carbenes, their Mixed Dimers and Organic Radicals

Published on: April 19, 2019

sp3-sp2 vs sp3-sp3 Selectividad del sitio C-C en la apertura del anillo catalizado por Rh del benzociclobutenol: un

Lina Ding¹, Naoki Ishida, Masahiro Murakami

¹Fukui Institute for Fundamental Chemistry, Kyoto University , Kyoto 606-8103, Japan.

Journal of the American Chemical Society

|December 18, 2013

Resumen

La apertura del anillo catalizado por Rh del benzociclobutenol favorece la escisión de enlaces C (sp) -C (sp) debido a la estabilización del estado de transición. La polaridad del disolvente y la masa de ligando influyen en la selectividad del sitio en este proceso clave de activación de enlaces C-C.

Área de la Ciencia:

Química organometálica Química orgánica de los metales.
Química computacional es la química computacional.
La catálisis de la catálisis.

Sus antecedentes:

Las reacciones catalizadas por Rh son cruciales para la activación del enlace C-C.
La apertura del anillo de benzociclobutenol presenta desafíos en la selectividad del sitio.
La comprensión de los mecanismos de reacción ayuda en el diseño de catalizadores.

Objetivo del estudio:

Investigar la selectividad del sitio en la apertura del anillo de benzociclobutenol catalizado por Rh.
Elucide los factores que rigen la escisión de los bonos C(sp(3)) -C(sp(2)) frente a C(sp(3)) -C(sp(3).
Determinar la influencia del disolvente y los ligandos en la selectividad.

Principales métodos:

Se emplearon cálculos de la Teoría Funcional de Densidad (DFT).
Se modeló el ciclo catalítico, incluida la transferencia de protones y la escisión C-C.
Se analizaron las energías e interacciones del estado de transición.

Principales resultados:

C(sp(3)) -C(sp(2)) la escisión es favorecida debido a la interacción anillo benceno-Rh estabilizando el estado de transición.
El aumento de la polaridad del disolvente (DMSO) reduce la selectividad al estabilizar el estado de transición C{\displaystyle C} -C{\displaystyle C} más.
Los ligandos DPPF voluminosos y los catalizadores atestados (Rh(P(t-Bu)3)2) disminuyen la selectividad debido al obstáculo estérico.

Conclusiones:

La selectividad del sitio está dictada principalmente por el paso de escisión del enlace C-C.
El diseño del catalizador, incluida la elección del ligando y el disolvente, es fundamental para controlar la selectividad.
Los catalizadores optimizados, como RhP(t-Bu) 3, pueden recuperar la selectividad a través de efectos estéricos.

Más Videos Relacionados

Efficient Construction of Drug-like Bispirocyclic Scaffolds Via Organocatalytic Cycloadditions of α-Imino γ-Lactones and Alkylidene Pyrazolones

Efficient Construction of Drug-like Bispirocyclic Scaffolds Via Organocatalytic Cycloadditions of α-Imino γ-Lactones and Alkylidene Pyrazolones

Published on: February 7, 2019

Preparation of Contiguous Bisaziridines for Regioselective Ring-Opening Reactions

Preparation of Contiguous Bisaziridines for Regioselective Ring-Opening Reactions

Published on: July 28, 2022

Videos de Conceptos Relacionados

Directing and Steric Effects in Disubstituted Benzene Derivatives

Directing and Steric Effects in Disubstituted Benzene Derivatives

When disubstituted benzenes undergo electrophilic substitution, the product distribution depends on the directing effect of both substituents. When the directing effects of both substituents reinforce each other, a single product is obtained. For example, bromination of p-nitrotoluene occurs ortho to the methyl group and meta to the nitro group, which is the same position, resulting in a single product. However, if the directing effects of the two groups oppose each other, the...

Regioselectivity and Stereochemistry of Acid-Catalyzed Hydration

Regioselectivity and Stereochemistry of Acid-Catalyzed Hydration

The rate of acid-catalyzed hydration of alkenes depends on the alkene's structure, as the presence of alkyl substituents at the double bond can significantly influence the rate.

Regioselectivity of Electrophilic Additions-Peroxide Effect

Regioselectivity of Electrophilic Additions-Peroxide Effect

In the presence of organic peroxides, the addition of hydrogen bromide to an alkene yields the isomer that is not predicted by Markovnikov’s rule. For example, the addition of hydrogen bromide to 2-methylpropene in the presence of peroxides gives 1-bromo-2-methylpropane. This addition reaction proceeds via a free radical mechanism, which reverses the regioselectivity. The free radical reaction mechanism involves three stages: initiation, propagation, and termination.

meta-Directing Deactivators: –NO2, –CN, –CHO, –&NoBreak;CO2R, –COR, –CO2H

meta-Directing Deactivators: –NO₂, –CN, –CHO, –⁠CO₂R, –COR, –CO₂H

All meta-directing substituents are deactivating groups. These substituents withdraw electrons from the aromatic ring, making the ring less reactive toward electrophilic substitution. For example, the nitration of nitrobenzene is 100,000 times slower than that of benzene because of the deactivating effect of the nitro group. The first step in an electrophilic aromatic substitution is the addition of an electrophile to form a resonance-stabilized carbocation. The energy diagrams for...

ortho–para-Directing Activators: –CH3, –OH, –&NoBreak;NH2, –OCH3

ortho–para-Directing Activators: –CH₃, –OH, –⁠NH₂, –OCH₃

All ortho–para directors, excluding halogens, are activating groups. These groups donate electrons to the ring, making the ring carbons electron-rich. Consequently, the reactivity of the aromatic ring towards electrophilic substitution increases. For instance, the nitration of anisole is about 10,000 times faster than the nitration of benzene. The electron-donating effect of the methoxy group in anisole activates the ortho and para positions on the ring and stabilizes the corresponding...

Benzene to 1,4-Cyclohexadiene: Birch Reduction Mechanism

Benzene to 1,4-Cyclohexadiene: Birch Reduction Mechanism

Birch reduction uses solvated electrons as reducing agents. The reaction converts benzene to 1,4-cyclohexadiene. The reaction proceeds by the transfer of a single electron to the ring to form a benzene radical anion. This anion is highly basic—it abstracts a proton from the alcohol to form a cyclohexadienyl radical. Another single electron transfer gives the cyclohexadienyl anion. A proton transfer from the alcohol forms 1,4-cyclohexadiene. Since this reduction occurs via radical anion...