The Malonic Ester Synthesis

by James

Description: The Malonic Ester Synthesis is a method for making substituted carboxylic acids. It is a combination of three reactions: 1) deprotonation, 2) alkylation, 3) acidic ester hydrolysis, and 4) decarboxylation.

Notes: This reaction is essentially the same as the acetoacetic ester synthesis (see also). Note that the base used is usually the same as the group that is lost from the ester (MeO(-) in this case).


Notes: Note that in each case one of the esters ends up being converted into carbon dioxide (CO2). The third example shows how the process can be used to make a disubstituted carboxylic acid. In the fourth example, the use of an alkyl halide with two halogens allows for two successive alkylation reactions, giving a cyclic product.


The malonic ester synthesis is composed of five parts: 1) deprotonation of the ester to give an enolate, 2) alkylation of the enolate with an alkyl halide, 3) hydrolysis of the ester under acidic conditions, 4) decarboxylation, and 5) tautomerization. Rather than draw out all of the steps readers are referred to each of these individual reactions.


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In the very first picture of the steps of the reaction, I think Na+ is missing from step one – but this was super helpful!


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