Q11 · 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
The major structures of A and B in the following reaction sequence are 
(a)A = 
B = 
B = (b)A = 
B = 
B = (c)A = 
B = 
B = (d)A = 
B = 
B = Answer
Answer: C ✓ checked by 4AB · confidence medium
Explanation
Grubbs ring-closing metathesis joins the N-allyl and the C-allyl chain, loses ethylene and closes a six-membered ring (N–CH₂–CH=CH–CH₂–C8a). This gives the bicyclic lactam A with the C=C retained between C-6 and C-7. LiAlH₄ then reduces only the lactam C=O to CH₂, so amine B keeps the C=C. Answer: (c).
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