ACID CATALYZED REARRANGEMENTS IN BICYCLONONANES 2-SUBSTITUTED-6-(1,3-DIOXOLAN-2-YL)CYCLOOCTANONES FROM 1-SUBSTITUTED-2-HYDROXY-9,9(ETHYLENEDIOXY)-BICYCLONONANES

Article abstract of DOI:10.1016/S0040-4020(01)96615-3

Treatment of endo-2 or exo-2-hydroxy-1-substituted ketals 1a-d with p-toluenesulfonic acid in dry benzene results in a reversible C₉ bridge cleavage and affords equilibrium mixtures where 2-substituted-6-(1,3-dioxolan-2-yl)-cyclooctanones 6a-d are present as main products.Yields in 6a-d increase as the steric hindrance of the substituents at C₁ in the substrate increases as well.Deuterium exchange experiments are in favour of an intramolecular 1,3-hydride shift from C₂ to C₉.