The 3-keto esters or β -keto esters are obtained by the Claisen condensation of two esters.

Diesters produce cyclic 3-ketoesters by intramolecular Claisen condensation, also called Dieckmann condensation
Mixed Claisen produces 1,3-dicarbonyl compounds by condensation between ketone and ester.
  • Obtaining 3-ketoesters

condensation claisen 1


condensation claisen 2

Ethyl 3-oxobutanoate (ethyl acetylacetate), can be obtained by Claisen from ethyl acetate, and is a very efficient reagent for the preparation of ketones.


Malonic synthesis is a method that allows obtaining carboxylic acids. This synthesis starts with diethyl propanedioate (diethyl malonate).


When the electrophile used in the acetylacetic or malonic synthesis is a,b -unsaturated, a 1,5-dicarbonyl will be formed, this type of reaction is called Michael addition.

michael addition 1

The use of aldehydes and ketones in the acetylacetic or malonic synthesis allows obtaining ketones or a,b -unsaturated acids.

condensation knoevenagel 1

Acyloinic condensation transforms esters into alpha-hydroxyketones. This reaction is carried out with sodium metal in an inert solvent.

acyloionic condensation 1

Benzoin condensation yields a -hydroxycarbonyls by reaction of aromatic aldehydes with sodium cyanide.

benzoinic condensation 01

The reaction of aldehydes with 1,3-dithiacyclohexane, in the presence of Lewis acids, produces 1,3-dithianes that have hydrogens that can be subtracted with strong bases, forming the 1,3-dithiane anion. These anions are very good nucleophiles and react with a wide range of electrophiles.

Let's see how to obtain 2-butanone from ethanal.
synthesis 13 days 01