PCC oxidizes the primary alcohol to an aldehyde without removing the remote alkene. ZnBr₂ activates that aldehyde for an intramolecular carbonyl-ene cyclization. A chair-like arrangement controls the new stereocentres, while allylic hydrogen transfer shifts the original alkene to an isopropenyl group. The favoured relative configuration has the methyl and hydroxyl groups on the same indicated face and the isopropenyl group opposite, as in C.
More 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. questions
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