Cyclic enol ether synthesis via arenesulfonyl iodide additions to alkynols

The reaction of arenesulfonyl iodides with alkynols generally provides adducts in good yields. Treatment of these adducts with KN(SiMe(3))(2) gives enol ethers; cyclisation of the functionalised pentenol (5) results in formation of the Exo-alkylidene tetrahydrofuran (7), whereas the homologous hexenol (6) gives the dihydropyran (8). Attempts to cyclise the hexenol (6) with potassium t-butoxide under the conditions reported by Short and Ziegler generally gave the endocyclic ether (8). Copyright (C) 1996 Elsevier Science Ltd