Accedi

Regular Claisen condensation involves the synthesis of β-ketoesters by combining identical ester molecules bearing two α hydrogens in the presence of an alkoxide base. The reaction commences with the deprotonation of the acidic α hydrogen by the base to form a resonance stabilized ester enolate. This nucleophilic ion then attacks the carbonyl center of another ester molecule to generate a tetrahedral alkoxide intermediate. Next, the expulsion of the alkoxide group from the intermediate restores the carbonyl center and produces an acyl-substituted ester. The alkoxide by-product subsequently abstracts the second α proton from the β-dicarbonyl compound to form a doubly-stabilized enolate ion. This step is the driving force of the reaction to completion and suggests the essential requirement of two α protons in starting ester. Finally, acidification of the enolate produces the desired β-ketoester. The utility of the Claisen condensation process is also observed in biological systems. For instance, the synthesis of acetoacetyl-CoA from the condensation of acetyl-CoA in the presence of thiolase enzyme.

Tags

Claisen CondensationketoestersEster EnolateNucleophilic AttackTetrahedral IntermediateAlkoxide GroupAcyl substituted EsterDicarbonyl CompoundEnolate IonAcidificationAcetoacetyl CoAThiolase Enzyme

Dal capitolo 15:

article

Now Playing

15.27 : Esters to β-Ketoesters: Claisen Condensation Mechanism

α-Carbon Chemistry: Enols, Enolates, and Enamines

3.4K Visualizzazioni

article

15.1 : Reattività degli Enoli

α-Carbon Chemistry: Enols, Enolates, and Enamines

2.8K Visualizzazioni

article

15.2 : Reattività degli ioni enolato

α-Carbon Chemistry: Enols, Enolates, and Enamines

2.3K Visualizzazioni

article

15.3 : Tipi di enoli ed enolati

α-Carbon Chemistry: Enols, Enolates, and Enamines

2.4K Visualizzazioni

article

15.4 : Convenzioni del Meccanismo Enolato

α-Carbon Chemistry: Enols, Enolates, and Enamines

1.9K Visualizzazioni

article

15.5 : Formazione regioselettiva di enolati

α-Carbon Chemistry: Enols, Enolates, and Enamines

2.4K Visualizzazioni

article

15.6 : Effetti stereochimici dell'enolizzazione

α-Carbon Chemistry: Enols, Enolates, and Enamines

1.9K Visualizzazioni

article

15.7 : α-alogenazione catalizzata da acido di aldeidi e chetoni

α-Carbon Chemistry: Enols, Enolates, and Enamines

3.4K Visualizzazioni

article

15.8 : α-alogenazione di aldeidi e chetoni promossa da basi

α-Carbon Chemistry: Enols, Enolates, and Enamines

3.3K Visualizzazioni

article

15.9 : Alogenazione multipla di metilchetoni: reazione di aloformio

α-Carbon Chemistry: Enols, Enolates, and Enamines

1.8K Visualizzazioni

article

15.10 : α-alogenazione dei derivati dell'acido carbossilico: panoramica

α-Carbon Chemistry: Enols, Enolates, and Enamines

3.2K Visualizzazioni

article

15.11 : α-Bromurazione degli acidi carbossilici: reazione di Hell-Volhard-Zelinski

α-Carbon Chemistry: Enols, Enolates, and Enamines

2.9K Visualizzazioni

article

15.12 : Reazioni dei composti α-alocarbonilici: sostituzione nucleofila

α-Carbon Chemistry: Enols, Enolates, and Enamines

3.1K Visualizzazioni

article

15.13 : Nitrosazione degli Enoli

α-Carbon Chemistry: Enols, Enolates, and Enamines

2.3K Visualizzazioni

article

15.14 : Formazione del legame C-C: Panoramica sulla condensazione aldolica

α-Carbon Chemistry: Enols, Enolates, and Enamines

13.3K Visualizzazioni

See More

JoVE Logo

Riservatezza

Condizioni di utilizzo

Politiche

Ricerca

Didattica

CHI SIAMO

Copyright © 2025 MyJoVE Corporation. Tutti i diritti riservati