| Dieckmann condensation | |
|---|---|
| Named after | Walter Dieckmann |
| Reaction type | Ring forming reaction |
| Identifiers | |
| Organic Chemistry Portal | dieckmann-condensation |
| RSC ontology ID | RXNO:0000065 |
TheDieckmann condensation is theintramolecularchemical reaction ofdiesters with base to give β-keto esters.[1] It is named after the German chemistWalter Dieckmann (1869–1925).[2][3] The equivalentintermolecular reaction is theClaisen condensation. Dieckmann condensations are highly effective routes to 5-, 6-, and 7-member rings, but poor for larger rings.[4]
Deprotonation of an ester at the α-position generates anenolate ion which then undergoes a5-exo-trig nucleophilic attack to give a cyclic enol. Protonation with aBrønsted–Lowry acid (H3O+ for example) re-forms the β-keto ester.[5]
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.[6]
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| Animation of the reaction mechanism |