Dieckmann condensation
The Dieckmann condensation is the intramolecular chemical reaction of diesters with base to give β-keto esters. It is named after the German chemist Walter Dieckmann. The equivalent intermolecular reaction is the Claisen condensation.
Reaction mechanism
Deprotonation of an ester at the α-position generates an enolate ion which then undergoes a 5-exo-trig nucleophilic attack to give a cyclic enol. Protonation with a Brønsted-Lowry acid re-forms the β-keto ester.Due to the steric stability of five- and six-membered rings, these structures will preferentially be formed. 1,6 diesters will form five-membered cyclic β-keto esters, while 1,7 diesters will form six-membered β-keto esters.
| Animation of the reaction mechanism |