The Al(OTf)(3)-catalyzed cycloisomerization of unactivated unsaturated alcohols was studied from experimental and theoretical points of view. A series of cyclic ethers was obtained in excellent yields and regioselectivities. This catalyst system provides one of the most straightforward routes to cyclic ethers with Markovnikov-type regioselectivity under mild conditions. Theoretical and NMR studies were carried out in order to better determine the mechanism of this reaction. The NMR studies were in agreement with preferential complexation of Al(OTf)(3) to the oxygen atom of the unsaturated alcohol, but did not exclude complexation to the double bond of the alcohol. Theoretical calculations indicated strong acidification of the hydroxyl proton when Al(OTf)(3) was complexed to the alcohol oxygen atom. A plausible catalytic cycle for the Al(OTf)(3)-catalyzed intramolecular hydroalkoxylation of unactivated olefins is proposed.

Cyclic voltammetry and preparative-scale electrochemical studies on the intramolecular cyclization of allyl 2-halophenyl ethers catalyzed by Ni(II)−cyclam complexes leads us to propose a mechanism involving Ni(I) and Ni(III) intermediate species. The role of Mg2+ ions in the reactivity and selectivity of the process is discussed. The Ni(cyclam)Br2-catalyzed electrosynthesis of dihydrobenzofurans and dihydrobenzopyrans from unsaturated side-chain aryl halide derivatives is effected in good yields in the presence of a magnesium anode.