Reaction of 3,5,5-trimethylcyclohex-2-en-1-one with NaNH2 ( 3 equiv) in THF generates an enolate

step 1 Hi guys, let's solve problem 8 .33. We need to propose a mechanism for the reaction between two

Reaction of 3,5,5-trimethylcyclohex-2-en-1-one with NaNH2 (...

Reaction of $3,5,5$-trimethylcyclohex-2-en-1-one with $\mathrm{NaNH}_{2}$ ( 3 equiv) in THF generates an enolate. When bromobenzene is added to this solution and stirred for $4 \mathrm{~h}$, a product 9-A is isolated in $30 \%$ yield. Formulate a mechanism for this reaction.

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Key Concepts

Enolate Formation

This concept involves the deprotonation of a carbonyl compound at its alpha position using a strong base. The resulting enolate ion is resonance stabilized and acts as a nucleophile. Recognizing enolate formation is crucial for understanding how carbon-carbon bonds are formed in many reactions, including Michael additions and other condensation reactions.

Benzyne Mechanism

Under strongly basic conditions, aromatic halides such as bromobenzene can undergo an elimination reaction to form a highly reactive benzyne intermediate. Benzyne features a strained triple bond within the aromatic ring, which can be attacked by nucleophiles. This mechanism explains substitutions on apparently unreactive aromatic systems and is a key alternative pathway in nucleophilic aromatic substitution.

Nucleophilic Aromatic Substitution

This type of substitution involves a nucleophile replacing a leaving group on an aromatic ring. When the aromatic substrate is not activated by electron-withdrawing groups, the reaction may proceed via a benzyne intermediate. Understanding this concept is essential for discerning how nucleophiles interact with aromatic rings under different conditions, particularly in the presence of a strong base.

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