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I. Peroxycarbenium ion-mediated C-C bond formation: A. Applications to synthesis of cyclic peroxides. B. Mechanistic investigations. II. Lewis acid-mediated hock rearrangement. III. Development of new oxidation systems
Abstract
The activation of peroxyacetals and dialkyl peroxides by Lewis acids is investigated. Intramolecular displacement of unsaturated peroxyacetals and peroxyketals in the presence of SnCl$\sb4$ or TiCl$\sb4$ forms 1,2-dioxanes, 1,2-dioxepanes, and 1,2-dioxacanes. Intermolecular displacements are shown to be capable of displacement of either the alkoxide or peroxide group with a selectivity dependent upon substrate, nucleophile, Lewis acid, and reaction temperature. Mechanistic investigations demonstrate that both the intra- and intermolecular displacements of peroxyacetals involve intermediate peroxycarbenium ions. Similar selectivity is observed in the Lewis acid-mediated allylation of dialkyl peroxides. Reaction in the presence of TiCl$\sb4$ leads to displacement of the peroxide by an allyl group through C-O ionization whereas use of SnCl$\sb4$ results in O-O heterolysis and skeletal rearrangement. Competition experiments and spectroscopic observation of Lewis acid/peroxide complexes by low temperature $\sp{13}$C and $\sp{119}$Sn NMR are used to probe the role of complexation and ionization in these reactions. Finally, the deliberate fragmentation of peroxyketals in the presence of Lewis acids or iodonium ions is investigated as an approach to peroxonium oxidants and the formation of hypochlorite hemiacetals from bleach and hexahaloacetones is shown to provide an efficient method for chlorination.
Subject Area
Organic chemistry
Recommended Citation
Lee, Hyung-Jae, "I. Peroxycarbenium ion-mediated C-C bond formation: A. Applications to synthesis of cyclic peroxides. B. Mechanistic investigations. II. Lewis acid-mediated hock rearrangement. III. Development of new oxidation systems" (1997). ETD collection for University of Nebraska-Lincoln. AAI9805513.
https://digitalcommons.unl.edu/dissertations/AAI9805513