Diastereoselective synthesis of tetrahydropyranes via Ag(i)-initiated dimerization of cinnamyl ethers

We present herein the first synthesis of tetrahydropyranes promoted by a silver salt. Cinnamyl ethers undergo a formal dimerization affording the target heterocycle via sequential C–O bond cleavage/C–H bond functionalization. The cascade allows one to assemble three new bonds and to establish up to four stereocenters. The reaction likely proceeds through a cationic manifold that forms the target in a diastereoselective fashion