Synthesis of Bicyclic Ethers by a Gold/Palladium/Gold-Catalyzed Cyclization/Cross Coupling Sequence

The stereoselective gold-catalyzed 6-endo cyclization. of various beta-hydroxyallenes in the presence of N-iodosuccinimide affords iodinated dihydropyrans in good yield. Subsequent functionalization by palladium-catalyzed cross coupling opens an access to alpha-hydroxyallenes that are converted in a second gold-catalyzed cyclization into furopyrans which occur in various natural products.