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Dieckmann Condensation

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    66507

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    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.

    350px-DieckmannCondensation.png

    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 Bronsted-Lowry acid (H3O+ for example) re-forms the β-keto ester.[6]

    635px-DieckmannCondensationMechanism.png

    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.[7]

    Dieckmann_startAnimGif_1.gif

    Animation of the reaction mechanism

    See also

    • Claisen condensation
    • Gabriel-Colman rearrangement

    References

    1. Dieckmann, W. Ber. 1894, 27, 102 & 965
    2. Dieckmann, W. Ber. 1900, 33, 595 & 2670
    3. Dieckmann, W. Ann. 1901, 317, 51 & 93
    4. Schaefer, J. P.; Bloomfield, J. J. (1967). "The Dieckmann Condensation (Including the Thorpe-Ziegler Condensation)". Organic Reactions. 15: 1–203. doi:10.1002/0471264180.or015.01.
    5. Davis, B. R.; Garrett, P. J. Comp. Org. Syn. 1991, 2, 806-829. (Review)
    6. Janice Gorzynski Smith (2007). Organic Chemistry (2nd ed.). pp. 932–933. ISBN 978-0073327495.
    7. "Dieckmann Condensation". Organic Chemistry Portal.

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