Q24 · 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 
$\text{A}\ \xrightarrow[\text{(ii) H}_3\text{O}^{+}\ \text{(iii) Zn-HCl}]{\text{(i) t-BuONO, NaOEt}}\ \text{B}$
$\text{A}\ \xrightarrow[\text{(ii) H}_3\text{O}^{+}\ \text{(iii) Zn-HCl}]{\text{(i) t-BuONO, NaOEt}}\ \text{B}$(a)A = 
B = 
B = (b)A = 
B = 
B = (c)A = 
B = 
B = (d)A = 
B = 
B = 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
NaOEt/2-bromobutane alkylates the active methylene (A). t-BuONO nitrosates the remaining α-H; acid cleaves the acetyl group (deacylation), leaving the α-oximino ester, which Zn/HCl reduces to the α-amino ester — ethyl isoleucinate, B in (c).
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