Q31 · CSIR-NET Chemistry, December 2019
Paper: CSIR-NET December 2019 · Subject: Organic Chemistry · Chapter: Reagents, Reaction Mechanisms & Named Reactions · Topic: Reagents, Reaction Mechanisms & Named Reactions – General · Marks: 2 · Difficulty: Medium
Under review — part of this question (a structure or an option) is not clear in the source scan. 4AB is checking it against the original book; the answer shown may change.
The major products A and B in the following transformation are: 
Answer
Under review — not yet confirmed.
Answer: D
The source book printed no answer; this one was worked out and checked — see the explanation.
Explanation
Only the Julia–Kocienski olefination (PT-sulfone, LiHMDS) gives the (E)-alkene selectively. The Wittig with a non-stabilised ylide gives mainly (Z); acid dehydration of 2-methylhexan-3-ol gives the more substituted 2-methylhex-2-ene; the acid-mediated Peterson from the drawn diastereomer gives the (Z)-isomer.
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