Cyclic peroxides using ozone

Because nowadays the ozonation reaction has reached industrial development maturity, being no longer only a laboratory curiosity, and because it rests on a sound mechanistic background, future applications are very likely to emerge. The stability of adequately-substituted secondary ozonides may lead to their use in medicine, although bioavailability problems may arise as in the case of compound 285 however, other cyclic peroxidic antimalarial compounds may be found <2007JMC2516>. 

Trioxirane is a cyclic isomer of ozone but whereas trioxirane has six 7f-electrons, ozone has only four. The relative positions of trioxirane and ozone on the O3 potential surface are of some interest and we have therefore carried out additional calculations in which the geometries of both species were optimized with the 4-31G basis set. This basis set gives more reasonable values of the 0—0 distances (1.468 A in hydrogen peroxide compared with the experimental value of 1.475 A, 1.476 A in trioxirane, and 1.255 A in ozone compared with the experimental value of 1.277 A). Using the 4-31G optimized geometries, ozone is calculated to be 18.0 kcal/mol more stable than trioxirane at the 6-31G level. Distortions Dsn -> Cz ) from the 4-3IG optimized structure for trioxirane lead to an increase in (4-3IG) energy, i.e. the cycUc structure is a local potential minimum in the 4-31G surface for O3 under a Czv symmetry constraint. 

The preparative use of the ozonization of cyclic olefins in methanol, which leads to eight-membered ring peroxides, has been discussed for the steroid series by Lettre and Hotz.148... 

Ozonolysis of cyclic alkenes gives dicarbonyl compounds. For example, treatment of cyclohexene in methanol with ozone, followed by addition of hydrogen peroxide gave adipic acid (5.101). Particularly useful are variants of this process that lead to differentiated functional groups, thereby making subsequent selective reactions feasible. Ozonolysis at low temperature followed by addition of... 

For any alkene, hydrogen peroxide may be used as the oxidizing agent and either dimethyl sulfide or zinc and acetic acid may be used as the reducing agent (see Chapter 18, Section 18.4.3). Ozonolysis of a cyclic alkene leads to oxidative cleavage to a diketone, a dialdehyde, a keto-aldehyde, a keto acid, or a dicarboxylic acid. When 1,3-dimethylcyclopentene (67) is treated with ozone and then with zinc and acetic acid, oxidative cleavage leads to keto-aldehyde 68 (2-ethyl-5-oxooctanal). 

Another type of epoxy oligomers are the cyclo-aliphatic ones, obtained by oxidation of cyclic diolefins with various peroxidic compounds (organic or inorganic hydroperoxides), hypochlorous acid, halogenhydrines and their derivatives, and oxygen or ozone. At present, the main industrial procedure for their production uses peracetic acid. In keeping with initial cycloolefin structure, diepoxides with different structures are produced, with the peculiarity that peroxidic oxygen is bound to the aliphatic cycle. 

The demand for white and coloured mbber articles for various applications is steadily growing. Rubbers are, depending on their content of olefinic double bonds, very sensitive to ozone, and hence effective antiozonants are necessary. Due to their discolouring and staining effect, para-phenylenediamine antiozonants cannot be used in compounds for white or coloured articles. A survey of the effectiveness of Vulkazon AFS, a cyclic acetal providing excellent ozone protection in coloured compounds based on various elastomers, is presented. The effectiveness of the cyclic acetal is compared with paraphenylenediamine antiozonants in chloroprene, butyl and halobutyl compounds. The effect in diene rubbers, where the cyclic acetal has to be used in combination with waxes, is investigated. Cyclic acetals do not affect the peroxide cure like other antiozonants and hence the material has also been tested in peroxide-cured cable jacket compounds based on a saturated elastomer. 2 refs. 

Ozonolysis of double bonds as a route to ketones and aldehydes is well known. Thiourea may be used for the reduction of the ozonide to afford aldehydes from suitable alkenes. Electrolytic reduction of ozonization products from the oxidation of trisubstituted cyclic alkenes in acetic acid offers a route to hydroxy-ketones. a-Alkoxy-peroxides, from ozonolysis in alcoholic solution, are stable... 

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