Q10 · CSIR-NET Chemistry, December 2018
Paper: CSIR-NET December 2018 · Subject: Organic Chemistry · Chapter: Reagents, Reaction Mechanisms & Named Reactions · Topic: Reagents, Reaction Mechanisms & Named Reactions – General · Marks: 2 · Difficulty: Easy
The correct sequence of reagents to be used for the following conversion is- 
(a)I) $\mathrm{LDA}, \mathrm{EtBr}$; II) EtLi ; III) $\mathrm{H}_{3} \mathrm{O}^{+}$
(b)I) EtLi ; II) $\mathrm{LDA}, \mathrm{EtBr}$; III) $\mathrm{H}_{3} \mathrm{O}^{+}$
(c)I) $\mathrm{H}_{3} \mathrm{O}^{+}$; II) EtLi ; III) LDA, EtBr
(d)I) EtLi ; II) $\mathrm{H}_{3} \mathrm{O}^{+}$; III) $\mathrm{LDA}, \mathrm{EtBr}$
Answer
Answer: A ✓ checked by 4AB · confidence high
Explanation
LDA/EtBr first alkylates C-6 of 3-methoxycyclohexenone. EtLi then adds 1,2 to the C=O, and H₃O⁺ triggers the Stork–Danheiser transposition. The product is the enone with Et on the β-carbon and on the adjacent γ-carbon (a).
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