In the reaction sequence,Cyclohex-2-en-1-one | vedclass

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Question

(A) The reaction of $\alpha, \beta$-unsaturated ketones with Grignard reagents $(RMgX)$ in the presence of a catalytic amount of copper $(I)$ salts (l

Vedclass · Accepted Answer

$3-$methylcyclohexanone

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(A) The reaction of $\alpha, \beta$-unsaturated ketones with Grignard reagents $(RMgX)$ in the presence of a catalytic amount of copper $(I)$ salts (like $CuCl$) leads to conjugate addition ($1$,$4$-addition) rather than direct addition ($1$,$2$-addition) to the carbonyl group.$1$. The $CuCl$ reacts with $CH_3MgBr$ to form an organocopper reagent $(CH_3Cu)$,which is a 'softer' nucleophile than the Grignard reagent.$2$. This softer nucleophile selectively attacks the softer electrophilic center,which is the $\beta$-carbon of the $\alpha, \beta$-unsaturated system.$3$. The initial product is an enolate,which upon aqueous workup $(H_2O/H^+)$ yields the saturated ketone,$3$-methylcyclohexanone.Therefore,the correct product $(X)$ is $3$-methylcyclohexanone.

In the reaction sequence,
$Cyclohex-2-en-1-one \xrightarrow[(ii) H_2O/H^+]{(i) CH_3MgBr/CuCl} (X)$
Product $(X)$ will be:

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In the reaction sequence,$Cyclohex-2-en-1-one \xrightarrow[(ii) H_2O/H^+]{(i) CH_3MgBr/CuCl} (X)$Product $(X)$ will be: