Q12 · CSIR NET Chemistry, December 2014
Paper: CSIR NET December 2014 · Subject: Organic Chemistry · Chapter: Reagents, Reaction Mechanisms & Named Reactions · Topic: Reagents, Reaction Mechanisms & Named Reactions – General · Marks: 2 · Difficulty: Easy
The major product formed in the following transformation is: 
2. $\mathrm{PhCHO}$
2. $\mathrm{PhCHO}$(a)
(b)
(c)
(d)
Answer
Answer: A ✓ checked by 4AB · confidence medium
Explanation
Bu₂BOTf/i-Pr₂NEt forms the Z-boron enolate, which undergoes an Evans syn-aldol through a Zimmerman–Traxler chair. The (4R,5S)-norephedrine-derived auxiliary sets the absolute configuration of the syn product (a).
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