Q25 · 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: Hard
The major product formed in the following reaction sequence is: 
(a)
(b)
(c)
(d)
Answer
Answer: C ✓ checked by 4AB · confidence high
The source book printed no answer; this one was worked out and checked — see the explanation.
Explanation
Danishefsky's diene and methyl pyruvate undergo a hetero-Diels–Alder reaction on the ketone C=O; TFA then eliminates MeOH to give the 2,3-dihydro-4H-pyran-4-one with Me and CO₂Me on C-2, the enone double bond adjacent to the ring oxygen — structure (c).
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