Peroxycarbenium-Mediated C−C Bond Formation:  Applications to the Synthesis of Hydroperoxides and Peroxides

Abstract

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 TiCl(4), SnCl(4), and trimethylsilyl triflate, peroxyacetals and peroxyketals undergo reaction with allyltrimethylsilane, silyl enol ethers, and silyl ketene acetals to afford homoallyl peroxides, 3-peroxyketones, and 3-peroxyalkanoates, respectively. Reactions of peroxyacetals are Lewis acid dependent; TiCl(4) promotes formation of ethers while SnCl(4) and trimethylsilyl triflate promote formation of peroxides. Lewis acid-promoted reactions of silylated hydroperoxyacetals furnish silylated hydroperoxides, which can be deprotected to homologated hydroperoxides. Hydroperoxyketals undergo Lewis acid-mediated allylation to furnish 1,2-dioxolanes via attack of hydroperoxide on the intermediate carbocation. Lewis acid-mediated cyclization of unsaturated peroxyacetals furnishes 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.

Re2O7-catalyzed reaction of hemiacetals and aldehydes with O-, S-, and C-nucleophiles

“…The results with peroxyhemiacetals are consistent with the known reactivity of bisperoxyacetals [26]. The hydroperoxyacetals showed no sign of electrophilic activation of the hydroperoxide (which would presumably lead to heterolytic fragmentation) and activation of the peroxide C–O was clearly disfavored relative to activation of the alkoxide C–O bond.…”

Stereoselective Allylation of Chiral Monoperoxyacetals.

“…Optimal conditions were found to involve addition of stoichiometric SnCl4 to a 0 °C solution of the peroxyacetal and allylsilane. 3 Reactions were generally complete within one to 2 h. The products were isolated and purifi ed by standard methods, with diastereoselectivity determined by NMR integration; control experiments demonstrated no difference in diastereomer ratios before or after purifi cation. Ether 12b and the pivaloate ester 12f reacted with moderate syn selectivity (vide infra); diastereoselection was reduced in the case of the acetate (12d) or benzoate (12e) and nonexistent for the silyloxy peroxyacetal (12a).…”

Synthesis of five- and six-membered cyclic organic peroxides: Key transformations into peroxide ring-retaining products

“…The first step results in the formation of peroxycarbenium ions 97 , which are trapped with allyltrimethylsilane under the formation of intermediate hydroperoxides 98 . Then either cyclic dioxolanes 99–102 or unsaturated compounds 103–107 are formed as the major reaction products depending on the nature of the substituents and the Lewis acid (Scheme 27, Table 9) [257]. …”

“…The intramolecular cyclization of unsaturated peroxyacetals 273a–d in the presence of TiCl 4 or SnCl 4 occurs via formation of peroxycarbenium ions to give methoxy- and chlorine-containing dioxanes 274a–d as the reaction products (Scheme 76) [257]. …”