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Ch. 22 - Condensations and Alpha Substitutions of Carbonyl Compounds
Wade - Organic Chemistry 9th Edition
Wade9th EditionOrganic ChemistryISBN: 9780135213728Non è quello che usi tu?Cambia libro di testo
Tutti i libri di testoWade 9th EditionCh. 22 - Condensations and Alpha Substitutions of Carbonyl CompoundsProblema 54
Capitolo 22, Problema 54

Show how an acetoacetic ester synthesis might be used to form a δ-diketone such as heptane-2,6-dione.

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Identify the starting material for the acetoacetic ester synthesis. The key reagent is ethyl acetoacetate (CH₃COCH₂COOEt), which contains both a ketone and an ester functional group, making it a versatile compound for this reaction.
Determine the alkyl halides needed to form the δ-diketone. In this case, the target molecule, heptane-2,6-dione, suggests that two alkyl groups (ethyl groups) need to be added to the central carbon of ethyl acetoacetate.
Perform the first alkylation. Deprotonate the methylene group (CH₂) of ethyl acetoacetate using a strong base such as sodium ethoxide (NaOEt) to form an enolate ion. Then, react the enolate with ethyl bromide (C₂H₅Br) to add the first ethyl group.
Perform the second alkylation. Repeat the process by deprotonating the remaining methylene hydrogen of the monoalkylated product with a strong base, forming a new enolate ion. React this enolate with another equivalent of ethyl bromide to add the second ethyl group.
Hydrolyze and decarboxylate the diethylated product. Treat the compound with aqueous acid (H₃O⁺) to hydrolyze the ester group to a carboxylic acid. Then, heat the resulting β-keto acid to induce decarboxylation, yielding the desired δ-diketone, heptane-2,6-dione.

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Acetoacetic Ester Synthesis

Acetoacetic ester synthesis is a method for forming ketones through the reaction of an acetoacetic ester with an alkyl halide. This process involves the enolate ion of the acetoacetic ester attacking the alkyl halide, leading to the formation of a new carbon-carbon bond. The resulting product can be hydrolyzed and decarboxylated to yield a diketone, making it a valuable reaction in organic synthesis.
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Synthesis of Amino Acids: Acetamidomalonic Ester Synthesis Example 2

Diketones

Diketones are organic compounds that contain two carbonyl groups (C=O) within the same molecule. They can exhibit unique chemical properties and reactivity due to the presence of these functional groups. In the case of heptane-2,6-dione, the diketone structure allows for various synthetic applications, including the formation of complex molecules and intermediates in organic chemistry.
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Diketones

Enolate Chemistry

Enolate chemistry involves the formation and reactivity of enolate ions, which are generated from carbonyl compounds through deprotonation. These enolate ions are nucleophilic and can participate in various reactions, such as alkylation and condensation. Understanding enolate chemistry is crucial for acetoacetic ester synthesis, as it enables the formation of new carbon-carbon bonds necessary for constructing diketones like heptane-2,6-dione.
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Formation of Enolates
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In Solved Problem 22-9, the target molecule was synthesized using a Michael addition to form the bond that is β,γ to the upper carbonyl group. Another approach is to use a Michael addition to form the bond that is β,γ to the other (lower) carbonyl group. Show how you would accomplish this alternative synthesis.

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Show how the following ketones might be synthesized by using the acetoacetic ester synthesis.

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Propose a mechanism for the conjugate addition of a nucleophile (Nuc:–) to acrylonitrile (H2C=CHCN) and to nitroethylene. Use resonance forms to show how the cyano and nitro groups activate the double bond toward conjugate addition.

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Show how cyclohexanone might be converted to the following δ-diketone (Hint: Stork).

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Propose a mechanism for the conjugate addition of a nucleophile (Nuc:–) to acrylonitrile (H2C=CHCN). Use resonance forms to show how the cyano activate the double bond toward conjugate addition.

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Domanda del libro di testo

Show how the following products might be synthesized from suitable Michael donors and acceptors.

(a)

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