A Multiple Five‐Membered‐Ring‐Selective Williamson Reaction as a Key Step in the Stereoselective Construction of 2,5‐Linked Oligo(tetrahydrofuran)s

Four tetrahydrofuran rings in one step can be constructed with the multiple five-mem-bered-ring-selective Williamson reaction (1 → 2). The tetratosylate 1 is obtained from the corresponding dialkyne by a reagent-controlled, diastereoselective dihy-droxylation. This reaction sequence opens up an efficient route to enantiomerically pure oligo(tetrahydrofuran)s.