An excess of elemental iodine in N, N-dimethylacetamide enables effective 3/iodanylium-de- hydronation of terminal alkenes with 3-iodopropene derivatives and hydrogen iodide formation within minutes at room temperature. The optimal molar ratio of iodine to substrate was decreased to 1: 1 when hydrogen iodide formed was oxidized on a platinum anode. The electrolytic oxidation recovers iodine as a reagent and diminishes the hydrogen ...