Tetrahydrofuran, tetrahydropyran and oxepane formation by cobaloxime π-cation cyclizations

Article abstract of DOI:10.1016/S0040-4039(98)00601-7

Studies are reported on the cyclization of (ω-hydroxy-β-hydroxyalkyl)cobaloximes (1, 2 and 3) to form 5,6 and 7-membered ring cyclic ethers (4, 5 and 6). Reversible cyclization and eventual irreversible alkene decomplexation (to form 7, 8 and 9) varied as a function of ring size. The practical consequence is that cyclizations to form 5 and 6 membered rings are feasible whereas formation of a 7 membered ring is not.