Electronically unfavorable addition of electron-deficient olefins to isochromenylium tetrafluoroborates initiated by C-1 O-glycosylation

Electronically unfavorable reactions between isochromenylium tetrafluoroborates and electron-deficient olefins have been studied and achieved by assistance of a phenolic hydroxyl group in the olefin substrates, providing the corresponding 2-oxabicyclo[3.3.1]nonane derivatives diastereoselectively in moderate to satisfactory yields. The new methodology is initiated by an intermolecular C-1 O-glycosylation, and completed with an intramolecular Michael addition and an aldol condensation in cascade fashion.