*** Welcome to piglix ***

Dieckmann condensation

Dieckmann condensation
Named after Walter Dieckmann
Reaction type Ring forming reaction
Identifiers
Organic Chemistry Portal dieckmann-condensation
RSC ontology ID RXNO:0000065

The Dieckmann condensation is the intramolecular chemical reaction of diesters with base to give β-ketoesters. It is named after the German chemist Walter Dieckmann (1869–1925). The equivalent intermolecular reaction is the Claisen condensation.

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 Bronsted-Lowry acid (H3O+ for example) re-forms the β-keto ester.

Owing to the steric stability of five- and six-membered ring structures, these will preferentially be formed. So 1,6 diesters will form five-membered cyclic β-keto esters, while 1,7 diesters will form six-membered β-keto esters.


...
Wikipedia

...