Video Experimental Relacionado

Updated: Jun 12, 2025

Facile Preparation of 2Z,4E-Dienamides by the Olefination of Electron-deficient Alkenes with Allyl Acetate

Facile Preparation of 2Z,4E-Dienamides by the Olefination of Electron-deficient Alkenes with Allyl Acetate

Published on: June 21, 2017

(Z) - Isomerización selectiva de alquenos 1,1-disubstituidos por activación de C-H alilico catalizado por el escandio

Shao-Jie Lou^1,2, Pan Wang³, Xin Wen³

¹Advanced Catalysis Research Group, RIKEN Center for Sustainable Resource Science, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.

Journal of the American Chemical Society

|September 20, 2024

Resumen

Este estudio introduce un nuevo método para la síntesis selectiva de alquenos (Z) -trisubstituidos a partir de alquenos 1,1-disubstituidos. El nuevo enfoque supera los desafíos de selectividad comunes, ofreciendo una ruta eficiente a compuestos orgánicos valiosos.

Área de la Ciencia:

Química orgánica
Catálisis
Metodología sintética

Sus antecedentes:

Los alquenos 1,1-disubstituidos pueden convertirse en alquenos trisubstituidos a través del desplazamiento de 1,3-hidrógeno.
Esta isomerización a menudo resulta en problemas desafiantes de regio y estereoselectividad, lo que produce mezclas de E / Z no deseadas o alquenos (E) termodinámicamente favorecidos.

Objetivo del estudio:

Desarrollar una isomerización altamente (Z) selectiva de alquenos 1,1-disubstituidos a alquenos (Z) trisubstituidos.
Para lograr la activación regiospecífica y estereospecífica de un enlace C-H alilico para la síntesis controlada de alquenos.

Principales métodos:

Utilizó un estérico exigente catalizador de medio sándwich de escandio.
Se utiliza 2-tert-butilquinolina como un aditivo voluminoso para controlar la selectividad.
Se realizaron experimentos de etiquetado de deuterio y cálculos de la teoría funcional de la densidad (DFT) para dilucidar el mecanismo.

Principales resultados:

Se logró una isomerización (Z) selectiva sin precedentes de alquenos 1,1-disubstituidos.
Demostró el papel crucial de la 2-ter-butilquinolina en la facilitación de la transposición del enlace C=C y en el control de la selectividad a través de la impedancia estérica.
Se han sintetizado con éxito diversos alquenos acíclicos y endocíclicos (Z) -trisubstituidos con alta regioselectividad y estereoselectividad.

Conclusiones:

Desarrolló un protocolo eficiente y selectivo para la síntesis de alquenos desafiantes (Z) -trisubstituidos.
El método exhibe un amplio alcance de sustrato y una eficiencia atómica del 100%.
La reacción se lleva a cabo a través de un mecanismo sin precedentes que implica una sinergia aditiva entre el catalizador y el control regioquímico y estereoquímico.

Más Videos Relacionados

Efficient Synthesis of All-Carbon Quaternary Centers via the Conjugate Addition of Functionalized Monoorganozinc Bromides

Efficient Synthesis of All-Carbon Quaternary Centers via the Conjugate Addition of Functionalized Monoorganozinc Bromides

Published on: May 26, 2019

Chemoselective Preparation of 1-Iodoalkynes, 1,2-Diiodoalkenes, and 1,1,2-Triiodoalkenes Based on the Oxidative Iodination of Terminal Alkynes

Chemoselective Preparation of 1-Iodoalkynes, 1,2-Diiodoalkenes, and 1,1,2-Triiodoalkenes Based on the Oxidative Iodination of Terminal Alkynes

Published on: September 12, 2018

Videos de Conceptos Relacionados

Regioselectivity of Electrophilic Additions to Alkenes: Markovnikov's Rule

Regioselectivity of Electrophilic Additions to Alkenes: Markovnikov's Rule

If a set of reactants can yield multiple constitutional isomers, but one of the isomers is obtained as the major product, the reaction is said to be regioselective. In such reactions, bond formation or breaking is favored at one reaction site over others.
The hydrohalogenation of an unsymmetrical alkene can yield two haloalkane products, depending on which vinylic carbon takes up the halogen. However, one product usually predominates, where hydrogen adds to the vinylic carbon bearing the...

[3,3] Sigmatropic Rearrangement of Allyl Vinyl Ethers: Claisen Rearrangement

[3,3] Sigmatropic Rearrangement of Allyl Vinyl Ethers: Claisen Rearrangement

The Claisen rearrangement is a [3,3] sigmatropic rearrangement of allyl vinyl ethers to unsaturated carbonyl compounds. The rearrangement is a concerted pericyclic reaction proceeding via a chair-like transition state.

E1 Reaction: Stereochemistry and Regiochemistry

E1 Reaction: Stereochemistry and Regiochemistry

One of the critical aspects of the E1 reaction mechanism, as also observed in E2, is the regiochemistry, with multiple regioisomers obtained as products. In the example discussed, the presence of water as a weak base favors elimination over substitution to generate two alkenes. Given that alkenes’ stability increases with the number of alkyl groups across the double bond, typically, E1 reactions lead to the Zaitsev product, for this is more substituted and stable than the Hofmann product.

E2 Reaction: Stereochemistry and Regiochemistry

E2 Reaction: Stereochemistry and Regiochemistry

Elimination reactions of alkyl halides can yield one or more alkenes depending on the specific regiochemical and stereochemical considerations. While the regiochemistry of the reaction governs the location of the double bond in the product, the stereochemical requirements often influence the geometry.
When a substrate with two different β hydrogens undergoes an E2 elimination, the presence of a strong base can yield two regioisomeric alkenes. The more-substituted alkene is the major...

Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation

Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation

Introduction
Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate.

Electrophilic Addition to Alkynes: Hydrohalogenation

Electrophilic Addition to Alkynes: Hydrohalogenation

Electrophilic addition of hydrogen halides, HX (X = Cl, Br or I) to alkenes forms alkyl halides as per Markovnikov's rule, where the hydrogen gets added to the less substituted carbon of the double bond. Hydrohalogenation of alkynes takes place in a similar manner, with the first addition of HX forming a vinyl halide and the second giving a geminal dihalide.