1.2.4- Trioxolanes ozonides

Ozone (332) generally combines with alkenes in a 1,3-dipolar fashion giving the so-called primary ozonides which recombine to 1,2,4-trioxolanes (ozonides). Its reaction with the parent MCP (1) is not known, whereas it reacts readily at... 

An inner-sphere electron reduction has been proposed as a possible mechanism for the Fe(II)-induced decomposition of 1,2,4-trioxolanes (ozonides) (75) and (76). Benzoic acid was found to be the major product. The nucleophilic Ee(II) species attack the ozonide from the less hindered side of the electrophilic 0-0 a orbital to generate exclusively the Ee(III) oxy-complexed radical (inner-sphere electron transfer). After selective scission of the C-C bond, the resulting carbon-centred radical produced the observed product. The substituent effect determine the regioselective generation of one of the two possible Fe(III)-complexed oxy radicals. The bond scission shown will occur if R is bulkier than R. ... 

An important paper by Salomon, Clennan and coworkers on dialkyl peroxides , where also one ozonide was reported, appeared in 1985. In this paper, a correlation among and 0 chemical shifts was established, and the influence of several factors like concentration, temperature, solvent and, naturally, chemical structure was thoroughly studied but confined to dialkyl peroxides. There was a gap of several years before the appearance of a further note reporting data of seven 1,2,4-trioxolanes (ozonides), 1-4, and of the 1,2,4,5-tetroxane 5. Their 0 NMR data are given in Table 2. Spectra were obtained at natural isotopic abundance, in toluene at 27 °C. 

Another case where orbital symmetry provides a useful insight is ozonolysis, which proceeds through a 1,2,3-trioxolane intermediate to a 1,2,4-trioxolane (ozonide) product. 

The PET reactions of oxiranes carried out in the presence of oxygen frequently produce oxygenated products such as 1,2,4-trioxolanes (ozonides). Futamura first reported that DCA-sensitized PET oxygenation of... 

Section II covers the synthesis of the cyclic peroxides with medium ring size from 5 to 7. Section HI covers the synthesis of 1,2,4-trioxanes. Classification in sub-sections and sub-sub-sections is done according to the type of reaction by which the cyclic peroxide system is formed. Syntheses of dioxirans, 1,2-dioxetanes, trioxolanes (ozonides), tetrox-anes, and macrocyclic peroxides are not discussed in this review. 

The initial product of the reaction between ozone and most olefins appears to be the 1,2,3-trioxolane ( ozonide ), which then collapses to a carbonyl compound and a zwitterionic intermediate, 68. In the presence of water, the intermediate hydroxy-hydroperoxide, 69, is produced and decomposes to additional carbonyl-containing compounds. 

Ozonation ofAlkenes. The most common ozone reaction involves the cleavage of olefinic carbon—carbon double bonds. Electrophilic attack by ozone on carbon—carbon double bonds is concerted and stereospecific (54). The modified three-step Criegee mechanism involves a 1,3-dipolar cycloaddition of ozone to an olefinic double bond via a transitory TT-complex (3) to form an initial unstable ozonide, a 1,2,3-trioxolane or molozonide (4), where R is hydrogen or alkyl. The molozonide rearranges via a 1,3-cycloreversion to a carbonyl fragment (5) and a peroxidic dipolar ion or zwitterion (6). 

The dipolar ion can react in several ways according to the solvent and the stmcture of the olefin. In inert solvents, if the carbonyl compound is highly reactive (eg, an aldehyde), the dipolar ion can be added to the carbonyl fragment to give the normal ozonide or 1,2,4-trioxolane (7) for example, 1,1-and 1,2-dialkylethylenes react in this manner. Tri- or tetraalkyl-substituted olefins produce a smaH, if any, yield of an ozonide when the ozonolysis is... 

Unsaturated compounds undergo ozonization to initially produce highly unstable primary ozonides (15), ie, 1,2,3-trioxolanes, also known as molozonides, which rapidly spHt into carbonyl compounds (aldehydes and ketones) and 1,3-zwitterion (16) intermediates. The carbonyl compound-zwitterion pair then recombines to produce a thermally stable secondary ozonide (17), also known as a 1,2,4-trioxolane (44,64,125,161,162). 

Propylene oxide — see Oxirane, methyl-Propylene ozonide — see 1,2,4-Trioxolane, 3-methyl-Propyliodone X-ray contrast and, 2, 520 Propynal... 

During ozonolysis of vinyl fluoride an explosive solid residue is produced, and the volatile ozonide, trapped at —63°C, may explode spontaneously or dining removal by syringe [1]. During the cryogenic distillation of the ozonide (formulated as a trioxolane), several explosions occurred, and the explosive reaction residue was destroyed by digestion with 5% potassium iodide solution for 24 h [2],... 

The preparation, properties and uses of ozonides have been reviewed comprehensively [1]. Many pure ozonides (trioxolanes) are generally stable to storage some may be distilled under reduced pressure. The presence of other peroxidic impurities is thought to cause the violently explosive decomposition often observed in this group [2], Use of ozone is not essential for their formation, as they are also produced by dehydration of c cF-dihydroxy peroxides [3], A very few isomeric linear trioxides (ROOOR) are known, they are also explosively unstable. Inorganic ozonides, salts of the radical C>3 anion, are also hazardous. 

Fluoroethylene ozonide, 0752 /rMaleic anhydride ozonide, 1406 f 2-Methyl-1,3-butadiene, Ozone, 1893 3-Methyl-l,2,4-trioxolane, 1235 trans-2-Pentene ozonide, 1982... 

Tang Y, Dong Y, WittUn S, Charman S A, ChoUet J, Chiu FCK, Charman WN, Matile H, Urwyler H, Dom A, Bajpai S, Wang X, Padmanilayam M, Karle JM, Brun R, Vennerstrom JL. (2007) Weak base dispiro-l,2,4-trioxolanes Potent antimalarial ozonides. Bioorg Med Chem Lett 17 1260-1265. 

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