 Ethyl acetoacetate

Ethyl acetoacetate is $\mathrm{C}{\mathrm{H}}_3\mathrm{COC}{\mathrm{H}}_2\mathrm{COOC}{\mathrm{H}}_2\mathrm{C}{\mathrm{H}}_3$, a beta-keto ester. Its central methylene group lies between two carbonyl-derived groups.

Delocalization stabilizes the corresponding enolate, making that carbon more acidic than an ordinary alkane carbon. This supports controlled carbon-carbon bond formation and subsequent transformations of the ester functionality.