Q12 · CSIR-NET Chemistry, June 2018
Paper: CSIR-NET June 2018 · Subject: Organic Chemistry · Chapter: Pericyclic Reactions · Topic: Electrocyclic · Marks: 2 · Difficulty: Hard
Mechanism of the following transformation involves 
+ 
+ (a)A [2+2] cycloaddition followed.by 'con' rotatory electrocyclic ring opening
(b)A [4+2] cycloaddition followed by 'con' rotatory electrocyclic ring opening
(c)A [4+2] cycloaddition followed by Cope-rearrangement
(d)A [2+2] cycloaddition followed.by 'dis' rotatory electrocyclic ring opening
Answer
Answer: D ✓ checked by 4AB · confidence high
Explanation
Photochemical [2+2] of DMAD-type alkyne with benzene gives a bicyclo[4.2.0]octatriene. Its thermal 6π ring opening is disrotatory and gives the cyclooctatetraene diester (d).
Study loop for Pericyclic Reactions