Hydroperoxide groups tetrahydrofurane

The same group reported additions of tetrahydrofuran or dioxolane 243 to alkynes 242b catalyzed by 10 mol% CuBr and using ferf-butyl hydroperoxide as the oxidant [337]. The reaction does not proceed in the absence of tert-butyl hydroperoxide however, CuBr was not essential as a catalyst, since the additions also proceeded in its absence, although reduced yields of products 244b were obtained. In the catalyzed process a two-electron cycle was proposed to operate since the reaction was not inhibited by BHT, while the uncatalyzed was as expected inhibited. It remains thus unclear what the role of CuBr is and how it is regenerated under the oxidative conditions (see above). 

With regards to oxidative reactivity, it seems that dicopper(II) end-on peroxo complexes are basic, or nucleophilic, in nature, without oxidizing substrates such as PPha or 2,4-di-tert-butylphenol. Instead, O2 is released and PPhs binds, or deprotonation of the phenol occurs leading to a Cu -hydroperoxide. By contrast, the side-on bound dicopper(II) peroxide and its isoelectronic isomer, the dicopper(III) bis(p-oxo) species, both are electrophilic and have been shown to react with a wide array of substrates, in intramolecular (ligand) oxidations, and intermolecular organic transformations. Our group has extended the oxidative capability of CU2O2 complexes to novel (for copper chemistry) substrates such as tetrahydrofuran and dimethylaniline, which are oxidized to 2-hydroxy-tetrahydrofuran, and methylaniline plus formaldehyde, respectively. 

This reaction differs from a simple cych2ation because of the introduction of the iodomethyl group in addition to ring formation, which is due to primary formation of an iodonium ion (2) and its intramolecular opening by the OH group. The reaction proceeds diastereoselectively giving rise to trans-2,5-disubstituted tetrahydrofurans 3. Tetrahydrofuran, often abbreviated as TH F, is a colorless, water-soluble hquid of pleasant odor, bp 64.5 °C. Inhalation of its vapors leads to severe poisoning. When stored in air, tetrahydrofuran is converted to a hydroperoxide by autoxidation ... 

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