Theory and Defination :


Acetoacetic-Ester Condensation is a chemical reaction where ethyl acetoacetate is alkylated at the α-carbon to both carbonyl groups and then converted into a ketone, or more specifically an α-substituted acetone. This is very similar to malonic ester synthesis.
Acetoacetic ester synthesis is a synthetic procedure used to convert a compound that has the general structural formula 1 into a ketone that has the general structural formula 2.

<img src="Acetoacetic-Ester-Condensation.jpg" alt="Acetoacetic-Ester Condensation"/>
where as,
R1 is alkyl group
L is Leaving group

The group -CH2COCH3 in 2 is contributed by an acetoacetic ester, hence the term acetoacetic ester synthesis.

<img src="Acetoacetic-Ester-Condensation.jpg" alt="Acetoacetic-Ester Condensation"/>  where R2 is alkyl , aryl group
Acetoacetic ester synthesis consists of four consecutive reactions that can be carried out in the same pot.
reaction 1: acid-base reaction
reaction 2: nucleophilic substitution
reaction 3: ester hydrolysis (using saponification)
reaction 4: decarboxylation
Taking an example as below ;

<img src="Acetoacetic-Ester-Condensation.jpg" alt="Acetoacetic-Ester Condensation"/>









As above mentioned follow the steps 

reaction 1: acid-base reaction
<img src="Acetoacetic-Ester-Condensation.jpg" alt="Acetoacetic-Ester Condensation"/>




reaction 2: nucleophilic substitution
<img src="Acetoacetic-Ester-Condensation.jpg" alt="Acetoacetic-Ester Condensation"/>





reaction 3: ester hydrolysis (using saponification)
<img src="Acetoacetic-Ester-Condensation.jpg" alt="Acetoacetic-Ester Condensation"/>





reaction 4: decarboxylation
<img src="Acetoacetic-Ester-Condensation.jpg" alt="Acetoacetic-Ester Condensation"/>






A more direct method to convert 3 to 4 is the reaction of 3 with the enolate ion (5) of acetone.
<img src="Acetoacetic-Ester-Condensation.jpg" alt="Acetoacetic-Ester Condensation"/>



However, the generation of 5 from acetone quantitatively in high yield is not an easy task because the reaction requires a very strong base, such as LDA, and must be carried out at very low temperature under strictly anhydrous conditions.
<img src="Acetoacetic-Ester-Condensation.jpg" alt="Acetoacetic-Ester Condensation"/>






Mechanism :


A strong base deprotonates the dicarbonyl α-carbon. This carbon is preferred over the methyl carbon because the formed enolate is conjugated and thus resonancestabilized. The carbon then undergoes nucleophilic substitution. When heated with aqueous acid, the newly alkylated ester is hydrolyzed to a β-keto acid, which isdecarboxylated to form a methyl ketone .

<img src="Acetoacetic-Ester-Condensation.jpg" alt="Acetoacetic-Ester Condensation"/>

<img src="Acetoacetic-Ester-Condensation.jpg" alt="Acetoacetic-Ester Condensation"/>

<img src="Acetoacetic-Ester-Condensation.jpg" alt="Acetoacetic-Ester Condensation"/>






Application with example :


1) Ethylaceto ester to phenyl propyl ketone

<img src="Acetoacetic-Ester-Condensation.jpg" alt="Acetoacetic-Ester Condensation"/>