What is the reaction that supports the keto and enol form of acetoacetate?

Ethyl acetoacetate is subject to keto-enol tautomerism. In the neat liquid at 33 °C, the enol consists of 15% of the total.

[3]

Ethyl acetoacetate is often used in theacetoacetic ester synthesis similar to diethyl malonate in the malonic ester synthesis or theKnoevenagel condensation. The protons alpha to carbonyl groups are acidic, and the resulting carbanion can undergo nucleophilic substitution. A subsequent thermal decarboxylation is also possible.

[4]

Similar to the behavior of acetylacetone, the enolate of ethyl acetoacetate can also serve as a bidentate ligand. For example, it forms purplecoordination complexes with iron(III) salts:

Ethyl acetoacetate can also be reduced to ethyl 3-hydroxybutyrate.

Ethyl acetoacetate, when heated alone (uncatalyzed) with benzyl alcohol, forms synthetically useful benzyl acetoacetate (benzyl groups being easily removed later by catalytic hydrogenolysis over Pd/C under neutral conditions), 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 synthesis of pyrroles, useful for porphyrin synthesis.

In organic chemistry, keto–enol tautomerism refers to a chemical equilibrium between a keto form (a ketone or an aldehyde) and an enol (an alcohol). The keto and enol forms are said to be tautomers of each other. Ketones contain a carbonyl group (a carbon-oxygen double bond). The simplest ketone is acetone (R = R' = methyl), with the formula CH3C(O)CH3. ... Examples include many sugars (ketoses), many steroids (e.g., testosterone), and the solvent acetone.