Theory and Defination :
The Dieckmann condensation is an
organic reaction used to form a carbon-carbon bond between two tethered ester
groups using an alkoxide base in alcohol to make a cyclic β-keto ester. This
reaction is essentially an intramolecular form of the Claisen condensation. One ester group of the starting
material must have an α-hydrogen which is abstracted by the base to form an
enolate and alcohol. The enolate then attacks the carbonyl carbon of another
ester molecule, an OR group is released to regenerate the base, and the final
β-keto ester product is formed. The product in base is then deprotonated again
to form another enolate intermediate and acid-workup is required to isolate the
final cyclic β-keto ester product.
General Reaction :
Mechanism :
The mechanism is similar to the Claisen Condensation.Adipic acid is treated with sodium ethoxide so that carbanion is formed.The carbanion attacks the carbonyl group of the same molecule (intramolecular condensation) forming cyclic product.Ethanol is removed once it is protonated and hence the product (2-Oxocyclopentene Carboxylate) is formed.
Examples and Application :
1.Synthesis of Tetronic Acids
from Esters
2. Synthesis of
4,4-Disubstituted Cyclohexane β-Keto Esters
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