Peroxycarbenium-mediated C-C bond formation: Applications to the synthesisof hydroperoxides and peroxides

The Lewis acid-mediated reaction of alkene nucleophiles with peroxyacetals provides an effective route for the synthesis of homologated peroxides and hydroperoxides. In the presence of Lewis acids such as TiCl4, SnCl4, and tr imethylsilyl triflate, peroxyacetals and peroxyketals undergo reaction with allyltrimethylsilane, silyl enol ethers, and silyl ketene acetals to affor d homoallyl peroxides, 3-peroxyketones, and 3-peroxyalkanoates, respectivel y. Reactions of peroxyacetals are Lewis acid dependent; TiCl4 promotes form ation of ethers while SnCl4 and trimethylsilyl triflate promote formation o f peroxides. Lewis acid-promoted reactions of silylated hydroperoxyacetals furnish silylated hydroperoxides, which can be deprotected to homologated h ydroperoxides. Hydroperoxyketals undergo Lewis acid-mediated allylation to furnish 1,2-dioxolanes via attack of hydroperoxide on the intermediate carb ocation. Lewis acid-mediated cyclization of unsaturated peroxyacetals furni shes 1,2-dioxanes, 1,2-dioxepanes, and 1,2-dioxacanes through 6-endo/exo, 7 -endo/endo, and 8-endo/endo pathways. The corresponding reactions involving 6-endo/endo and 5-endo/exo pathways were unsuccessful.