Gold(I)-Catalyzed Synthesis of Dihydropyrans

A trinuclear gold(I)-oxo complex, (Ph3PAu)3OBF4, serves as the catalyst for the stereocontrolled synthesis of 2-hydroxy-3,6-dihydropyrans from propargyl vinyl ethers. Importantly, the rearrangement proceeds with excellent diastereoselectivity, and the rearrangement of chiral nonracemic propargyl vinyl ethers proceeds with excellent chirality transfer to furnish enantioenriched pyrans. Additionally, the reaction is amenable to the synthesis of spiroketals from appropriately functionalized precursors. In this case, from a linear precursor, in a single step, the bicyclic spiroketal framework is established with complete stereocontrol over three centers and an alkene functional group in the product.