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Imine Metathesis by Silica-Supported Catalysts Using the Methodology of Surface Organometallic Chemistry
Published on: October 18, 2019
Reacciones catalíticas de formación de enlaces carbono-carbono mediadas por silicio de amidas no activadas
Shū Kobayashi1, Hiroshi Kiyohara, Miyuki Yamaguchi
1Department of Chemistry, School of Science, University of Tokyo, and The HFRE Division, ERATO, Japan Science Technology Agency, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan. shu_kobayashi@chem.s.u-tokyo.ac.jp
Journal of the American Chemical Society
|December 22, 2010
Resumen
Este estudio introduce un nuevo método catalítico para sintetizar adutos de tipo Mannich utilizando amidas e iminas no activadas. Este avance permite reacciones de adición de tipo directo eficientes, expandiendo las posibilidades sintéticas en química orgánica.
Área de la Ciencia:
- Química orgánica es la química orgánica.
- La catálisis es la catálisis.
- Metodología sintética de la metodología sintética.
Sus antecedentes:
- Los enolados de silicio son reactivos establecidos en la síntesis orgánica.
- Las reacciones de adición catalítica directa que involucran amidas son menos comunes.
- Las amidas no activadas generalmente requieren condiciones más duras para la funcionalización.
Objetivo del estudio:
- Desarrollar un método catalítico para la adición directa de amidas no activadas a las iminas.
- Para lograr altos rendimientos y estereoselectividades en la formación de adutos tipo Mannich.
- Para explorar la utilidad catalítica de las especies de silicio en la funcionalización de amida.
Principales métodos:
- Reacción de amidas no activadas con iminas.
- Utilizando cantidades catalíticas de triacilcilcil triflato y trietilamina.
- Empleando enolados de silicio generados in situ.
Principales resultados:
- Se lograron altos rendimientos y altas anti-selectividades de aductos de tipo Mannich.
- Demostró el primer uso catalítico de especies de silicio para esta transformación.
- Empleó con éxito amidas con alfa-protones menos ácidos en adición directa.
Conclusiones:
- Se ha desarrollado una nueva y eficiente reacción catalítica de tipo Mannich utilizando amidas no activadas.
- Este método representa un avance significativo en las reacciones de adición catalítica de tipo directo.
- Los ensayos preliminares de catálisis asimétrica muestran potencial para la síntesis enantioselectiva.
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01:29Preparation of Amides
Amides are synthesized by treating carboxylic acids with amines in the presence of dehydrating agents like dicyclohexylcarbodiimide (DCC).
The DCC-promoted synthesis of amides begins with the protonation of DCC by carboxylic acid. The protonation makes it a better acceptor. Next, the addition of carboxylate to the protonated carbodiimide gives a reactive acylating agent.
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The DCC-promoted synthesis of amides begins with the protonation of DCC by carboxylic acid. The protonation makes it a better acceptor. Next, the addition of carboxylate to the protonated carbodiimide gives a reactive acylating agent.
Subsequently, the amine acts as a nucleophile that attacks the acylating agent to form a tetrahedral intermediate. In the...
01:28Amides to Carboxylic Acids: Hydrolysis
Amides can undergo either acid-catalyzed hydrolysis or base-promoted hydrolysis through a typical nucleophilic acyl substitution. Each hydrolysis requires severe conditions.
Acid-catalyzed hydrolysis:
Hydrolysis of amides under acidic conditions yields carboxylic acids. Since the reaction occurs slowly, hydrolysis requires the conditions of heat.
The mechanism begins with the protonation of the carbonyl oxygen by the acid catalyst. The protonation makes the amide carbonyl carbon more...
Acid-catalyzed hydrolysis:
Hydrolysis of amides under acidic conditions yields carboxylic acids. Since the reaction occurs slowly, hydrolysis requires the conditions of heat.
The mechanism begins with the protonation of the carbonyl oxygen by the acid catalyst. The protonation makes the amide carbonyl carbon more...
01:26Preparation of 1° Amines: Hofmann and Curtius Rearrangement Mechanism
The Hofmann and Curtius rearrangement reactions can be applied to synthesize primary amines from carboxylic acid derivatives such as amides and acyl azides. In the Hofmann rearrangement, a primary amide undergoes deprotonation in the presence of a base, followed by halogenation to generate an N-haloamide. A second proton abstraction produces a stabilized anionic species, which rearranges to an isocyanate intermediate via an alkyl group migration from the carbonyl carbon to the neighboring...
01:19Amines to Amides: Acylation of Amines
Various carboxylic acid derivatives (such as acid chlorides, esters, and anhydrides) can be used for the acylation of amines to yield amides. The reaction requires two equivalents of amines. The first amine molecule functions as a nucleophile and attacks the carbonyl carbon to produce a tetrahedral intermediate. This is followed by the loss of the leaving group and restoration of the C=O bond.
Next, the second equivalent of amine serves as a Brønsted base and deprotonates the quaternary amide...
Next, the second equivalent of amine serves as a Brønsted base and deprotonates the quaternary amide...
01:16Aldehydes and Ketones with Amines: Imine and Enamine Formation Overview
Primary amines react with carbonyl compounds—aldehydes and ketones—to generate imines. Imines consist of a C=N double bond and are named Schiff bases after its discoverer—the German chemist Hugo Schiff. On the other hand, secondary amines react with carbonyl compounds to give enamines. In enamines, the presence of a C=C double bond adjacent to the nitrogen atom leads to the delocalization of the lone pair.
02:27Preparation of Alkynes: Alkylation Reaction
Introduction
Alkylation of terminal alkynes with primary alkyl halides in the presence of a strong base like sodium amide is one of the common methods for the synthesis of longer carbon-chain alkynes. For example, treatment of 1-propyne with sodium amide followed by reaction with ethyl bromide yields 2-pentyne.
Alkylation of terminal alkynes with primary alkyl halides in the presence of a strong base like sodium amide is one of the common methods for the synthesis of longer carbon-chain alkynes. For example, treatment of 1-propyne with sodium amide followed by reaction with ethyl bromide yields 2-pentyne.