Curtis, Richard John; (1990) Synthesis and reactions of some cyclic peroxides. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

A series of 1,2-dioxanes was prepared with the intention of studying the effect of substituents upon their rearrangement/decomposition. The synthesis of the 1,2-dioxanes involves mercury (II) salt mediated cyclizations of appropriate δ,ϵ-unsaturated hydroperoxides followed by reductive demercuration. In this way, the 3-methyl-1,2-dioxanes:3-methyl-5-phenyl-1,2-dioxane, 3,6-dimethyl-5-phenyl-1,2-dioxane, 3,6-dimethyl-3-phenyl-1,2-dioxane, 3,3,6-trimethyl-1,2-dioxane, 3,3,6,6-tetramethyl-1,2-dioxane, 5-ethenyl-3-methyl-1,2-dioxane, and 3-methyl-1,2-dioxane itself were prepared; of which, five are novel. The 1,2-dioxanes were subjected to flash vacuum pyrolysis (fvp), to treatment with iron(II) sulphate, and in a limited number of cases, to photolysis. In all reactions a preference for rearrangement via 1,5-transfer of a hydrogen from C-3 or C-6 to an oxygen centred radical was observed. In the case of 5-ethenyl-3-methyl-1,2-dioxane, the 1,5-hydrogen transfer product was not isolated because of a novel tandem decarbonylation. Two other areas of cyclic peroxide chemistry were investigated. These were the cycloperoxyhalogenation of γ,δ-unsaturated hydroperoxides and the synthesis and reactions of diene hydroperoxides. The reaction of γ,δ-unsaturated hydroperoxides with N-iodosuccinimide (NIS), N-bromosuccinimide (NBS), bromine and iodine each gave the corresponding 3-halogenomethyl-1,2-dioxolane. The cyclization with NIS was found to have a wholly radical mechanism and that with halogen a wholly polar mechanism, whereas the NBS reaction was found to have both radical and polar components. A novel diene hydroperoxide capable of both 5-exo and 6-exo cyclizations was prepared and its reactions with a variety of reagents studied. Radical cyclization afforded the 1,2-dioxolanes in a regio- and stereo-specific manner, whereas polar cyclizations gave both 1,2-dioxanes and 1,2-dioxolanes.

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