Beta-iodoallenolates as springboards for annulation reactions.

β-Iodoallenolates II, generated from alkynones I with tetra-n-butylammonium iodide and a Lewis acid, underwent selective single or double annulation, depending on the Lewis acid promoter. Treatment with TiCl4 gave cyclohexenyl alcohols III, whereas BF3·OEt2 gave oxadecalins IV. The scope and limitations of the two annulation reactions are described.