Fatty acids,part 38: Neighbouring group participation in the oxymercuration-demercuration reaction. Another route to 1,4- and 1,5-epoxides

Oxymercuration-demercuration of hydroxy alkenes follows an intramolecular pathway to furnish 1,4-epoxides (tetrahydrofurans) when the hydroxyl group is β (trans only) or γ to a double bond and 1,5-epoxides (tetrahydropyrans) when the hydroxyl group is δ to the double bond. The cis and trans isomers of methyl ricinoleate and methyl 9-hydroxyoctadec-12-enoate, and a series of cis and trans octadecenols (Δ2–Δ6) are used to establish these relationships.1,4- and 1,5-Epoxides are also formed during the oxymercuration of methyl densipolate and methyl 12,13-dihydroxyoleate and during the hydroxymercuration of methyl octadeca-9,12 and 8,12-dienoates.