Ethyl acetoacetate

The organic compound ethyl acetoacetate (EAA) is the ethyl ester of acetoacetic acid. It is a colorless liquid. It is widely used as a chemical intermediate in the production of a wide variety of compounds.

Preparation
At large scale, ethyl acetoacetate is industrially produced by treatment of diketene with ethanol.

The small scale preparation of ethyl acetoacetate is a classic laboratory procedure. It involves Claisen condensation of ethyl acetate. Two moles of ethyl acetate condense to form one mole each of ethyl acetoacetate and ethanol.
 * Claisen ethyl acetate.png

Reactivity
Ethyl acetoacetate is subject to keto-enol tautomerism. In the neat liquid at 33 °C, the enol consists of 15% of the total. The enol is moderately acidic. Thus ethyl acetoacetate behaves similarly to acetylacetone:
 * CH3C(O)CH2CO2Et + NaH → CH3C(O)CH(Na)CO2Et + H2

The resulting carbanion undergoes nucleophilic substitution. Ethyl acetoacetate is often used in the acetoacetic ester synthesis, comparable to diethyl malonate in the malonic ester synthesis or the Knoevenagel condensation. After its alkylation and saponification, thermal decarboxylation is also possible. Like acetylacetone, ethyl acetoacetate affords ketoenolate complexes

The dianion of ethylacetoacetate is also a useful building block, except that the electrophile adds to the terminal carbon. The strategy can be depicted in the following simplified form:
 * CH3C(O)CH(Na)CO2Et + BuLi → LiCH2C(O)CH(Na)CO2Et + BuH
 * LiCH2C(O)CH(Na)CO2Et + RX → RCH2C(O)CH(Na)CO2Et + LiX

Reduction of ethyl acetoacetate gives ethyl 3-hydroxybutyrate.

Ethyl acetoacetate transesterifies to give benzyl acetoacetate via a mechanism involving acetylketene. Ethyl (and other) acetoacetates nitrosate readily with equimolar sodium nitrite in acetic acid, to afford the corresponding oximinoacetoacetate esters. A dissolving-zinc reduction of these in acetic acid in the presence of ketoesters or beta-diketones constitute the Knorr pyrrole synthesis, useful for the preparation of porphyrins.