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GATE 2023 CY – Question 39

Organic Chemistry · Oxidation: Oxidation of alcohols involving metal and non-metal-based (chromium, manganese, DMSO, and hypervalent iodine) reagents. Peracid oxidation of alkenes and carbonyls. Alkenes to diols (manganese and osmium-based reagents), alkenes to carbonyls with bond cleavage (ozonolysis), and alkenes to alcohols/carbonyls without bond cleavage (hydroboration-oxidation). Asymmetric epoxidations (Sharpless and Jacobsen) and Sharpless asymmetric hydroxylation. · 2 marks · Multiple choice

M and N in the given reaction scheme are

Diagram for GATE 2023 CY question 39
  1. Structure A
  2. Structure B
  3. Structure C
  4. Structure D

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Show answer and explanation

Correct answer: (C) Structure C

Explanation

Simmons–Smith cyclopropanation is directed by coordination of the allylic OH to zinc, so the CH2 bridge is delivered syn to the existing down-face OH groups. The cyclopropane hydrogens therefore point up. Osmium syn-dihydroxylation approaches the less hindered opposite face, placing the new OH pair up. The combined pair is **C**.