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Crossed Claisen Condensation

  • Page ID
    39397
  • Crossed Claisen condensation is a variation of Claisen condensation.

    Claisen Condensation:

    Crossed Claisen Condensation:

    eg:

    mechanism:
    Step 1: The alkoxide ion deprotanates the enolizable ester reversibly.

    Step 2 and 3: Enolate ion 1 undergoes a nucleophilic acyl substitution preferentially with the non-enolizable ester, which has the sterically less hindered and, therefore, more accessible carbonyl carbon, giving a β-ketoester.

    Step 4: The alkoxide ion deprotonates the β-ketoester irreversibly.

    Step 5: The acid protonates enolate ion 2

    see also Dieckmann condensation