In the reaction sequence [X] the major product respectively, are: · ABC26OR0673
Subject: Organic Chemistry · Chapter: Reagents, Reaction Mechanisms & Named Reactions · Topic: Reagents, Reaction Mechanisms & Named Reactions – General · Exam: GATE 2000-2022 · Marks: 2 · Difficulty: Medium
In the reaction sequence 
[X] 
the major product respectively, are:
[X] the major product respectively, are:(a)
and 
and (b)
and 
and (c)
and 
and (d)
and 
and Answer
Answer: A ✓ checked by 4AB · confidence low
Explanation
LDA/PhSeCl puts SePh on the α-carbon from the convex (exo) face of the cis-fused bicyclic lactone. LDA/MeI then regenerates the enolate and methylates it, again from the convex face. So in X, Me is exo (wedged, same side as the ring-fusion H's) and SePh is endo (hashed). H₂O₂ oxidises Se to the selenoxide, which eliminates syn. The ring-fusion H on the β-carbon is trans to SePh and cannot take part; only the methyl H's are syn, so Y is the exocyclic α-methylene lactone. Answer (a).
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