Q12 · CSIR-NET Chemistry, December 2015
Paper: CSIR-NET December 2015 · 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 structures of A and B in the following reaction sequence are 
(a)
(b)
(c)
(d)
Answer
Under review — not yet confirmed.
Answer: D
Explanation
Ph₃P then NaH converts 1,2-dibromoethane into vinyltriphenylphosphonium bromide (A); the phenoxide of salicylaldehyde adds to it (Michael) and the resulting ylide does an intramolecular Wittig with the aldehyde, giving 2H-chromene (d).
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