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GATE 2023 CY – Question 38

Organic Chemistry · Pericyclic Reactions and Photochemistry: Electrocyclic, cycloaddition and sigmatropic reactions. Diels-Alder reaction, Claisen and Cope rearrangements and their applications in organic synthesis. FMO method of analysis. Woodward-Hoffmann rules. Photochemistry of alkenes, arenes and carbonyl compounds. Photo-oxidation and photo-reduction. Di-π-methane rearrangements, Norrish type-I and II reactions. Paternό-Büchi reaction, Photo- Curtius and Wolff rearrangements. Barton and Hofmann-Lӧffler-Freytag reactions. · 2 marks · Multiple choice

E and F in the given reaction scheme are

Diagram for GATE 2023 CY question 38
  1. Structure A
  2. Structure B
  3. Structure C
  4. Structure D

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Show answer and explanation

Correct answer: (A) Structure A

Explanation

Photolysis cleaves the weak N–O bond and reorganizes the isoxazole into an acyl-substituted 2H-azirine, E. On heating, azirine opening and ring closure generate the oxazole with O adjacent to the phenyl-bearing carbon and N at the fused side. This atom order matches **A**; B exchanges the heteroatoms.