Video Experimental Relacionado

Updated: Sep 28, 2025

Preparation of a Corannulene-functionalized Hexahelicene by CopperI-catalyzed Alkyne-azide Cycloaddition of Nonplanar Polyaromatic Units

Preparation of a Corannulene-functionalized Hexahelicene by CopperI-catalyzed Alkyne-azide Cycloaddition of Nonplanar Polyaromatic Units

Published on: September 18, 2016

Adiciones fotocicloactivas selectivas y cooperativas en hojas aromáticas multistrada

Bappaditya Gole¹, Brice Kauffmann², Arnaud Tron³

¹Univ. Bordeaux, CNRS, Bordeaux Institut National Polytechnique, CBMN (UMR 5248), 2 rue Escarpit, 33600 Pessac, France.

Journal of the American Chemical Society

|April 5, 2022

Resumen

Los investigadores diseñaron nuevos pliegues de oligoamida fotosensibles con estructuras de hélice-hoja-hélice. Estas moléculas exhiben conformaciones controlables y fotoreacciones ordenadas, lo que permite modificaciones estructurales precisas.

Área de la Ciencia:

Química supramolecular
Síntesis orgánica
La fotoquímica

Sus antecedentes:

Los foldameros de oligoamida son valiosos para crear arquitecturas moleculares definidas.
Las unidades fotosensibles ofrecen un control dinámico sobre la estructura y la función molecular.
El control de la conformación y la reactividad de los pliegues es crucial para los materiales avanzados.

Objetivo del estudio:

Diseñar y sintetizar foldamuros aromáticos de oligoamida que incorporen unidades de diazaantraceno fotosensibles.
Para investigar el comportamiento conformacional y fotorreactividad de estos foldamers.
Demostrar la capacidad de orquestar fotorreacciones secuenciales para una modificación estructural controlada.

Principales métodos:

Síntesis de foldameros de oligoamida con un número variable de unidades fotosensibles.
Espectroscopia de resonancia magnética nuclear (RMN) y cristalografía de rayos X para el análisis estructural.
Reacciones fotoquímicas [4 + 4] de cicloadición para inducir cambios estructurales.

Principales resultados:

Los Foldamers adoptaron distintas conformaciones hélice-hoja-hélice basadas en el número de unidades de giro (par contra impar).
Las poblaciones conformacionales eran sintonizables a través del control del disolvente, la temperatura y la maniobrabilidad de la hélice.
Las unidades de diazaantraceno exhibieron fotorreactividad selectiva, permitiendo reacciones secuenciales programadas.
Las fotorreacciones condujeron al alargamiento y al endurecimiento de la estructura, con fotoproductos reversibles.

Conclusiones:

Se desarrollaron con éxito nuevos foldamers fotosensibles con plegamiento predecible y fotorreactividad ajustable.
Las fotorreacciones secuenciales se pueden controlar con precisión, lo que permite modificaciones estructurales específicas.
Estos hallazgos abren vías para el diseño de sistemas supramoleculares dinámicos y sensibles.

Más Videos Relacionados

Photogeneration of N-Heterocyclic Carbenes: Application in Photoinduced Ring-Opening Metathesis Polymerization

Photogeneration of N-Heterocyclic Carbenes: Application in Photoinduced Ring-Opening Metathesis Polymerization

Published on: November 29, 2018

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

Videos de Conceptos Relacionados

Cycloaddition Reactions: Overview

Cycloaddition Reactions: Overview

Cycloadditions are one of the most valuable and effective synthesis routes to form cyclic compounds. These are concerted pericyclic reactions between two unsaturated compounds resulting in a cyclic product with two new σ bonds formed at the expense of π bonds. The [4 + 2] cycloaddition, known as the Diels–Alder reaction, is the most common. The other example is a [2 + 2] cycloaddition.

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.

Thermal and Photochemical Electrocyclic Reactions: Overview

Thermal and Photochemical Electrocyclic Reactions: Overview

Electrocyclic reactions are reversible reactions. They involve an intramolecular cyclization or ring-opening of a conjugated polyene. Shown below are two examples of electrocyclic reactions. In the first reaction, the formation of the cyclic product is favored. In contrast, in the second reaction, ring-opening is favored due to the high ring strain associated with cyclobutene formation.

Photochemical Electrocyclic Reactions: Stereochemistry

Photochemical Electrocyclic Reactions: Stereochemistry

The absorption of UV–visible light by conjugated systems causes the promotion of an electron from the ground state to the excited state. Consequently, photochemical electrocyclic reactions proceed via the excited-state HOMO rather than the ground-state HOMO. Since the ground- and excited-state HOMOs have different symmetries, the stereochemical outcome of electrocyclic reactions depends on the mode of activation; i.e., thermal or photochemical.
Selection Rules: Photochemical Activation

Thermal Electrocyclic Reactions: Stereochemistry

Thermal Electrocyclic Reactions: Stereochemistry

The stereochemistry of electrocyclic reactions is strongly influenced by the orbital symmetry of the polyene HOMO. Under thermal conditions, the reaction proceeds via the ground-state HOMO.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.