Intramolecular Claisen Condensation
- This type of condensation uses diesters, just as diketones are used in the intramolecular aldol condensation.
- Below is an example for the mechanism of intramolecular claisen condensation:
- The cyclization works best with 1,6-diesters which give 5 membered cyclic beta-keto esters, and 1,7-diesters which give 6 membered cyclic beta-keto esters
- The mechanism for the dieckmann cyclization is analogous to that of the claisen condensation reaction.
- Firstly one of the two esters is converted into an enolate ion.
- This enolate then attacks the second ester via nucleophilic acyl substitution resulting in a cyclic beta-keto ester.
- Ester condensation is reversible thus the reaction is controled by thermodynamic constraints.
- Therefore only the most stable enolate proceeds to form a product.
- In this example the diester A is only converted into B which is a stable enolate, whereas C is not formed as it is not stable.
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Author: Eric Sanders (document modification date: 3rd December