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Acetoacetic Ester Synthesis

[ "article:topic", "authorname:ggunawardena" ]
  • Page ID
    16553
  • Acetoacetic ester synthesis is a synthetic procedure used to convert a compound that has the general structural formula 1 into aketone that has the general structural formula 2.

    acetoaceticestersynthesis1.png

    • R1 = alvikyl
    • L = leang group

    The group —CH2COCH3 in 2 is contributed by an acetoacetic ester, hence the term acetoacetic ester synthesis.

    acetoaceticestersynthesis2.png

     

    • R2 = alkyl, aryl

    Acetoacetic ester synthesis consists of four consecutive reactions that can be carried out in the same pot.

    • reaction 1: acid-base reaction
    • reaction 2: nucleophilic substitution
    • reaction 3: ester hydrolysis (using saponification)
    • reaction 4: decarboxylation

    eg:

    acetoaceticestersynthesis3.png

    reaction 1:

    acetoaceticestersynthesis4.png

    reaction 2:

    acetoaceticestersynthesis5.png

    reaction 3:

    acetoaceticestersynthesis6.png

    reaction 4:

    acetoaceticestersynthesis7.png

    A more direct method to convert 3 to 4 is the reaction of 3 with the enolate ion (5) of acetone.

    acetoaceticestersynthesis8.png

    However, the generation of 5 from acetone quantitatively in high yield is not an easy task because the reaction requires a very strong base, such as LDA, and must be carried out at very low temperature under strictly anhydrous conditions.

    acetoaceticestersynthesis9.png

    Acetoacetic ester synthesis provides a more convenient alternative to convert 3 to 4.

    Acetoacetic ester synthesis can be adapted to synthesize compounds that have the general structural formula 6.
     

    R3, R4 = identical or different alkyl groups

    eg:

    acetoaceticestersynthesis11.png

    reaction 1:

    acetoaceticestersynthesis12.png

    reaction 2:

    acetoaceticestersynthesis13.png

    reaction 1 (repeat):

    acetoaceticestersynthesis14.png

    reaction 2 (repeat):

    acetoaceticestersynthesis15.png

    reaction 3:

    acetoaceticestersynthesis16.png

    reaction 4:

    acetoaceticestersynthesis17.png