Q75 · CSIR-NET Chemistry, December 2016
Paper: CSIR-NET December 2016 · Subject: Organic Chemistry · Chapter: Pericyclic Reactions · Topic: Sigmatropic Shifts · Marks: 2 · Difficulty: Medium
The correct sequence of pericyclic reactions involved in the following transformation is 
(a)(i) ene reaction, (ii) [2,3]-sigmatropic shift, (iii) [3,3]-sigmatropic shift
(b)(i) ene reaction, (ii) [3,3]-sigmatropic shift, (iii) [1,3]-sigmatropic shift
(c)(i) [2,3]-sigmatropic shift, (ii) ene reaction, (iii) [1,3]-sigmatropic shift
(d)(i) [1,3]-sigmatropic shift, (ii) [2,3]-sigmatropic shift, (iii) [3,3]-sigmatropic shift
Answer
Answer: A ✓ checked by 4AB · confidence high
Explanation
SeO₂ allylic oxidation: an ene reaction with SeO₂ gives the allylseleninic acid, which undergoes a [2,3]-sigmatropic shift to the allylic selenite ester and hydrolysis to the allylic alcohol; a subsequent [3,3] (Claisen/Cope) completes the sequence before PCC oxidation.
Study loop for Pericyclic Reactions