Video Experimental Relacionado

Updated: Jun 22, 2026

Application of Elemental Lanthanides in the Selective C-F Activation of Trifluoromethylated Benzofulvenes Providing Access to Various Difluoroalkenes

Application of Elemental Lanthanides in the Selective C-F Activation of Trifluoromethylated Benzofulvenes Providing Access to Various Difluoroalkenes

Published on: July 28, 2018

La ciclopropanación catalizada por el trilato de lantano (III) a través de la transferencia intramolecular de

David J Hardee¹, Tristan H Lambert

¹Department of Chemistry, Columbia University, New York, New York 10027, USA.

Journal of the American Chemical Society

|June 4, 2009

Resumen

Un nuevo método catalizado por La(OTf)(3) permite una eficiente transferencia intramolecular de metileno de los epóxidos a las olefinas para la síntesis de ciclopropano. Este proceso logra una alta estereoselectividad y puede integrarse en estrategias de síntesis asimétricas.

Área de la Ciencia:

Química orgánica es la química orgánica.
La catálisis es la catálisis.
Metodología sintética de la metodología sintética.

Sus antecedentes:

Los anillos de ciclopropano son motivos valiosos en productos farmacéuticos y productos naturales.
Los métodos eficientes y estereoselectivos para la síntesis de ciclopropano son muy buscados.
Las reacciones intramoleculares ofrecen ventajas en el control de la estereoquímica y la eficiencia.

Objetivo del estudio:

Desarrollar un nuevo método catalítico para la ciclopropanación.
Para lograr una transferencia de metileno intramolecular eficiente y estereoselectiva.
Para demostrar la utilidad de este método en síntesis asimétrica.

Principales métodos:

Desarrollo de una reacción de ciclopropanación catalizada por triflato de lantano (La(OTf) ((3)).
Utilizando la transferencia intramolecular de metileno de un epoxido a una olefina.
Investigando el alcance del sustrato y los aspectos mecánicos.
Combinando la epoxidación enantioselectiva con el protocolo de ciclopropanación para una síntesis asimétrica.

Principales resultados:

Se desarrolló con éxito un nuevo método de ciclopropanación catalizado por La(OTf) ((3)).
La reacción procede con buena eficiencia y alta estereoselectividad.
Se demostró que una variedad de sustratos eran compatibles con las condiciones de reacción.
Se propuso una lógica mecanicista para la estereoselectividad observada.
Se demostró una síntesis asimétrica efectiva de ciclopropano.

Conclusiones:

El método desarrollado proporciona una ruta eficiente a los ciclopropanos a través de la transferencia intramolecular de metileno.
El sistema catalítico ofrece un alto control estereoquímico.
Esta metodología es una valiosa adición al kit de herramientas del químico sintético para la construcción de moléculas complejas.

Más Videos Relacionados

Accessing Valuable Ligand Supports for Transition Metals: A Modified, Intermediate Scale Preparation of 1,2,3,4,5-Pentamethylcyclopentadiene

Accessing Valuable Ligand Supports for Transition Metals: A Modified, Intermediate Scale Preparation of 1,2,3,4,5-Pentamethylcyclopentadiene

Published on: March 20, 2017

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: 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.

Alkenes via Reductive Coupling of Aldehydes or Ketones: McMurry Reaction

Alkenes via Reductive Coupling of Aldehydes or Ketones: McMurry Reaction

The radical dimerization of ketones or aldehydes gives vicinal diols through a pinacol coupling reaction. However, the behavior of titanium metals used for the reaction as a source of electrons is unusual. When the reaction is carried out in the presence of titanium, diols can be isolated at low temperatures. Else titanium further reacts with diols, forming alkenes through the McMurry reaction.

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.

Hydroboration-Oxidation of Alkenes

Hydroboration-Oxidation of Alkenes

In addition to the oxymercuration–demercuration method, which converts the alkenes to alcohols with Markovnikov orientation, a complementary hydroboration-oxidation method yields the anti-Markovnikov product. The hydroboration reaction, discovered in 1959 by H.C. Brown, involves the addition of a B–H bond of borane to an alkene giving an organoborane intermediate. The oxidation of this intermediate with basic hydrogen peroxide forms an alcohol.

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.

α-Alkylation of Ketones via Enolate Ions

α-Alkylation of Ketones via Enolate Ions

Ketones with α protons are deprotonated by strong bases like lithium diisopropylamide (LDA) to form enolate ions. The anion is stabilized by resonance, and its hybrid structure exhibits negative charges on the carbonyl oxygen and the α carbon. This ambident nucleophile can attack an electrophile via two possible sites: the carbonyl oxygen, known as O-attack, or the α carbon, known as C-attack. The nucleophilic attack via the carbanionic site is preferred. This is due to the strong interaction...