The base-catalyzed intramolecular condensation of a diester. The Dieckmann Condensation works well to produce 5- or 6-membered cyclic ß-keto esters, and is usually effected with sodium alkoxide in alcoholic solvent.
The yields are good if the product has an enolizable proton; otherwise, the reverse reaction (cleavage with ring scission) can compete. See the Claisen Condensation.
Mechanism of the Dieckmann Condensation
The mechanism is similar to the Claisen Condensation.
An Efficient and Scalable One-Pot Double Michael Addition-Dieckmann Condensation for the Synthesis of 4,4-Disubstituted Cyclohexane β-Keto Esters
M. R. DeGraffenreid, S. Bennett, S. Caille, F. Gonzalez-Lopez de Turiso, R. W. Hungate, L. D. Julian, J. A. Kaizerman, D. L. McMinn, D. Sun, X. Yan, J. P. Powers, J. Org. Chem., 2007, 72, 7455-7458.