Show how Claisen condensations could be used to make the following compounds.
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Step 1: Identify the target compound as a β-keto ester, which is a common product of Claisen condensation. The structure contains two carbonyl groups: one ketone and one ester, separated by a single carbon atom.

Step 2: Recall the general mechanism of Claisen condensation. It involves the reaction of two ester molecules (or an ester and a ketone) in the presence of a strong base, typically an alkoxide, to form a β-keto ester.

Step 3: Determine the starting materials. For this compound, the starting materials could be ethyl acetate (an ester) and cyclohexanone (a ketone). Cyclohexanone provides the cyclic ketone structure, while ethyl acetate contributes the ester group.

Step 4: Outline the reaction conditions. The reaction requires a strong base, such as sodium ethoxide (NaOEt), in an ethanol solvent. The base deprotonates the α-hydrogen of cyclohexanone, forming an enolate ion, which then attacks the carbonyl carbon of ethyl acetate.

Step 5: Describe the final steps of the reaction. After the nucleophilic attack, the intermediate undergoes elimination of the ethoxide group, forming the β-keto ester product. Acidic workup is typically performed to neutralize the reaction mixture and isolate the product.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Claisen Condensation

Claisen condensation is a reaction between two esters or an ester and a carbonyl compound in the presence of a strong base, leading to the formation of a β-keto ester or a β-diketone. This reaction involves the nucleophilic attack of an enolate ion on the carbonyl carbon of another ester, followed by the elimination of an alcohol. Understanding this mechanism is crucial for synthesizing complex organic molecules.

Enolate Ion

An enolate ion is a resonance-stabilized anion formed from a carbonyl compound, typically an aldehyde or ketone, when it is deprotonated at the alpha carbon. This ion acts as a nucleophile in various reactions, including Claisen condensation. The ability to generate and utilize enolate ions is fundamental in organic synthesis, allowing for the formation of carbon-carbon bonds.

Carbonyl Compounds

Carbonyl compounds, characterized by the presence of a carbonyl group (C=O), include aldehydes, ketones, and carboxylic acids. They are pivotal in organic chemistry due to their reactivity and ability to undergo various transformations, such as nucleophilic addition and condensation reactions. Recognizing the structure and reactivity of carbonyl compounds is essential for understanding the Claisen condensation and its applications in synthesizing complex molecules.

Show how Claisen condensations could be used to make the following compounds.(c)