Video Experimental Relacionado

Updated: Jul 2, 2026

Synthesis and Characterization of Supramolecular Colloids

Synthesis and Characterization of Supramolecular Colloids

Published on: April 22, 2016

Las adiciones fotociclo [2 + 2] intramoleculares controladas con disolventes de enonas alfa sustituidas

Stephanie M Ng¹, Scott J Bader, Marc L Snapper

¹Department of Chemistry, Merkert Chemistry Center, Boston College, 2609 Beacon Street, Chestnut Hill, Massachusetts 02467, USA.

Journal of the American Chemical Society

|June 1, 2006

Resumen

La elección del disolvente influye críticamente en el resultado de las adiciones fotociclo [2 + 2] intramoleculares en 2′-hidroxienonas. Los disolventes proteicos alteran la selectividad al interrumpir los enlaces de hidrógeno, lo que lleva a diferentes configuraciones de productos.

Área de la Ciencia:

Química orgánica es la química orgánica.
La fotoquímica es la fotoquímica.
Mecanismos de reacción Mecanismos de reacción

Sus antecedentes:

Las adiciones fotociclo [2 + 2] intramoleculares son reacciones clave en la síntesis orgánica.
El papel de los enlaces de hidrógeno en la dirección de las reacciones fotoquímicas es un área de investigación activa.

Objetivo del estudio:

Para investigar la regio- y estereoselectividad dependiente del disolvente de las adiciones fotociclo [2 + 2] intramoleculares de 2′-hidroxienonas.
Para dilucidar la influencia de la unión de hidrógeno intramolecular en las vías de reacción.

Principales métodos:

Las reacciones fotoquímicas se llevaron a cabo en varios disolventes apróticos y próticos.
El análisis del producto implicó la determinación de la selectividad regional y diastereológica.

Principales resultados:

Los disolventes apróticos favorecen la fotocicloadición a través de la unión de hidrógeno intramolecular.
Los disolventes protóticos rompen los enlaces de hidrógeno intramoleculares, lo que lleva a una diastereoselectividad complementaria.
La formación de regioisómeros (cabeza a cola frente a cabeza a cabeza) depende de la accesibilidad del disolvente y la olefina.

Conclusiones:

La polaridad del disolvente y la capacidad de enlace de hidrógeno controlan significativamente el resultado estereoquímico de estas adiciones de fotociclo.
La comprensión de estos efectos disolventes permite la síntesis dirigida de regiones específicas y estereoisómeros.

Más Videos Relacionados

Scale-up Chemical Synthesis of Thermally-activated Delayed Fluorescence Emitters Based on the Dibenzothiophene-S,S-Dioxide Core

Scale-up Chemical Synthesis of Thermally-activated Delayed Fluorescence Emitters Based on the Dibenzothiophene-S,S-Dioxide Core

Published on: October 24, 2017

Controlled Photoredox Ring-Opening Polymerization of O-Carboxyanhydrides Mediated by Ni/Zn Complexes

Controlled Photoredox Ring-Opening Polymerization of O-Carboxyanhydrides Mediated by Ni/Zn Complexes

Published on: November 21, 2017

Videos de Conceptos Relacionados

Halogenation of Alkenes

Halogenation of Alkenes

Halogenation is the addition of chlorine or bromine across the double bond in an alkene to yield a vicinal dihalide. The reaction occurs in the presence of inert and non-nucleophilic solvents, such as methylene chloride, chloroform, or carbon tetrachloride.
Consider the bromination of cyclopentene. Molecular bromine is polarized in the proximity of the π electrons of cyclopentene. An electrophilic bromine atom adds across the double bond, forming a cyclic bromonium ion intermediate.

Electrophilic Addition of HX to 1,3-Butadiene: Thermodynamic vs Kinetic Control

Electrophilic Addition of HX to 1,3-Butadiene: Thermodynamic vs Kinetic Control

The addition of a hydrogen halide to 1,3-butadiene gives a mixture of 1,2- and 1,4-adducts. Since more substituted alkenes are more stable, the 1,4-adduct is expected to be the major product. However, the product distribution is strongly influenced by temperature; low temperature favors the 1,2-adduct, whereas the 1,4-adduct is predominant at high temperature.

[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction

[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction

The Diels–Alder reaction is an example of a thermal pericyclic reaction between a conjugated diene and an alkene or alkyne, commonly referred to as a dienophile. The reaction involves a concerted movement of six π electrons, four from the diene and two from the dienophile, forming an unsaturated six-membered ring. As a result, these reactions are classified as [4+2] cycloadditions.

Electrophilic 1,2- and 1,4-Addition of X2 to 1,3-Butadiene

Electrophilic 1,2- and 1,4-Addition of X₂ to 1,3-Butadiene

Electrophilic addition of halogens to alkenes proceeds via a cyclic halonium ion to form a 1,2-dihalide or a vicinal dihalide.

Cycloaddition Reactions: MO Requirements for Thermal Activation

Cycloaddition Reactions: MO Requirements for Thermal Activation

Thermal cycloadditions are reactions where the source of activation energy needed to initiate the reaction is provided in the form of heat. A typical example of a thermally-allowed cycloaddition is the Diels–Alder reaction, which is a [4 + 2] cycloaddition. In contrast, a [2 + 2] cycloaddition is thermally forbidden.

Cycloaddition Reactions: MO Requirements for Photochemical Activation

Cycloaddition Reactions: MO Requirements for Photochemical Activation

Some cycloaddition reactions are activated by heat, while others are initiated by light. For example, a [2 + 2] cycloaddition between two ethylene molecules occurs only in the presence of light. It is photochemically allowed but thermally forbidden.