Ozonides oxidative cleavage

Perfluoroalkyl ethylene, CF3(CF2CF2) CH=CH2, obtained by dehalogena-tion of perfluoroalkylethyl iodide, is treated with ozone to give ozonides. Oxidative cleavage of the ozonides with hydrogen peroxide yields perfluoroalkanoic acids [132]. 

Beside being a source of C-22 chemicals, erucic acid is a natural source of C-13 and C-9 chemicals made by cleavage at the site of the double bond. Ozonolysis of erucic acid followed by oxidative cleavage of the ozonide to form brassylic acid (BA) and pelargonic acid (Chart I) has been demonstrated on the pilot plant scale.[2,3] Yield of 99% pure brassylic acid was 72 to 82% of theoretical. 

NOC1 and an alcohol 9-9 From ozonides 9-10 Oxidative cleavage of enol ethers 9-13 Reaction between carboxylic acids and lead tetraacetate 9-18 Oxidation of ethers 9-22 Oxidation of primary alcohols or aldehydes... 

Ozonolysis of cyclic olefins in the presence of carbonyl compounds gives the corresponding cross-ozonides.1329 In the ozonation of 1,2,4,5-tetramethyl-1,4-cyclohexadiene, oxidative dehydrogenation (formation of 1,2,4,5-tetramethylben-zene) was found to compete with oxidative cleavage because of steric hindrance.1330 Secondary ozonides (the 76 1,2,4-trioxolanes) are formed in high yields in the gas-phase, low-temperature ozonation of terminal and disubstituted alkenes.1331... 

The oxidative cleavage of ozonides leads to carboxylic acids. This cleavage is carried out by treatment of the crude ozonization product with alkaline silver oxide, potassium permanganate, or hydrogen peroxide solution,121 or with peracetic acid.122... 

If the reaction is carried out in an emulsion of sodium hydroxide and hydrogen peroxide, the ozonide inteimediaies are convoted to carboxylic acids directly, with a consequent increase in yields. Oxidative cleavage of y-hydroxyalkenes results in the formation of lactones in good yields (equation... 

The literature of this reaction to 1940 has been adequately reviewed. The emphasis up to that time was placed on obtaining higher yields of carbonyl compounds by hydrolysis of the ozonides. Several methods have been described for the oxidative cleavage of ozonides to acids. These procedures may prove valuable in the synthesis of certain acids. By adding the ozonide of 1-tridecene to an alkaline silver oxide suspension at 95°, a 94% yield of lauric acid is obtained. Decomposition of ozonides with 30% hydrogen peroxide is described for the preparation of 5-methyl-hexanoic acid (67%) from 6-methyl-l-heptene and of adipic acid (60%) from cyclohexene. A study of solvents for ozonolysis has been made. ... 

Oxidative cleavage is commonly carried out with O3, followed by cleavage of the intermediate ozonide with H2O. 

The oxidative cleavage of ozonides to carboxylic acids is achieved with hydrogen peroxide in sodium hydroxide solution [97], in formic acid... 

Ozonides are hardly ever isolated. Rather, conversions to products of ozonolysis are carried out in the same reaction vessels see Oxidative Cleavage of Double Bonds, page 77). 

Better yields are often obtained when ozone is used for oxidative cleavage of olefins to carboxylic acids or of cycloalkenes to dicarboxylic acids. Olefinic double bonds are very much more easily attacked by ozone than are aromatic systems, so that arylethylene derivatives can be successfully treated with ozone without appreciable effect on the ring. If the ozonide which is formed initially is decomposed with water, the aldehyde is obtained together with hydrogen peroxide and other products ... 

For future labeling syntheses of potential biosynthetic precursors, as well as for preparation of monocyclic diketones 70, on a 100- to 1000-g scale, additional, nonbiomimetic syntheses to these important intermediates were elaborated (63) (see Scheme 14). The key step of the first synthesis was oxidative cleavage of suitably substituted dimethyl indenes 68, either directly with permanganate-periodate or via remarkably stable ozonides 69. The required indenes 68 could be prepared from esters 67, and thus from very cheap educts like methacrylic acid and... 

Using modern analytical methods, a number of transient intermediates and byproducts could be verified [19, 20]. The first step in the mechanism of ozonolysis is the 1,3-dipolar cycloaddition of the dipole ozone to the double bond of OA. A 1,2,3-trioxolane is formed, the unstable primary ozonide or molozonide. The primary ozonide collapses in a 1,3 dipolar cycloreversion to a carbonyl compound and a carbonyl oxide, the so-called Criegee zwitterion. Since OA is substituted with two diverse groups at the double bond, two different opportunities exist for the formation of carbonyl compound and carbonyl oxide. Again, a 1,3-dipolar cycloaddition of these intermediates leads to three different pairs of 1,2,4-trioxolane derivatives (cisltram), the secondary ozonides, which are more stable than the primary ones. Their oxidative cleavage results in AA and PA. 

Ozonolysis (Sections 8.16B and 8.19) The oxidative cleavage of a multiple bond using O3 (ozone). The reaction leads to the formation of a cychc compound called an ozonide, which is then reduced to carbonyl compounds by treatment with dimethyl sulfide (M02S) or zinc and acetic acid. 

To explain this observation, experiments have shown that 2,3-dimethyl-butene reacts with ozone to give 140 by initial dipolar addition however, a rearrangement occurs to give 139, which is commonly called an ozonide. When 139 is treated with aqueous hydrogen peroxide in a second chemical step, two molar equivalents of acetone are formed. The overall transformation cleaved both bond of the C=C unit, converting each carbon to a carbonyl. The overall process is called oxidative cleavage and will be elaborated in Chapter 17, Section 17.4. 

If the focus is on the C=C unit of 2,3-dimethyl-2-butene, the dipolar addition reaction cleaves the first bond (the n-bond), and the rearrangement of the 1,2,3-trioxolane to the 1,2,4-trioxolane cleaves the second bond (the c-bond). The conversion of an alkene to an ozonide is known as ozonolysis, and it is an example of an oxidative cleavage reaction. The ozonide is usually not isolated, but a second chemical step is performed in the same flask. When treated with hydrogen peroxide, the products of this reaction are 2-propanone (acetone) and a second molecule of acetone. This statement is phrased this way because an unsymmetrical alkene will give two different ketones. In effect, the C=C unit is cleaved and each carbon is oxidized to a C=0 unit. The mechanism described for this reaction is consistent with known chemistry of ketones and aldehydes and other carbonyl-bearing functional groups. A full discussion of carbonyl chemistry will be presented in Chapters 17 and 19. 

Oxidative cleavage of an alkene with ozone leads to an ozonide. Reductive workup with dimethyl sulfoxide or zinc and acetic acid gives ketones and/or aldehydes. Oxidative workup with hydrogen peroxide gives ketones and/or carboxylic acids. Oxidative cleavage of 1,2-diols with periodic acid or with lead tetraacetate gives aldehydes or ketones. 

Ozonolysis of lycopadiene followed by oxidative cleavage of the ozonide afforded 6,10,14-trimethylpentadecan-2-one thus establishing the C(14)-C(15) and C(18)-C(19) location of the unsaturations. Moreover, the optical rotation of this ketone was identical with that observed for the 6(R),10(R), 14-trimethylpentadecan-2-one obtained from ozonolysis of natural phytol this result allowed assignment of stereochemistry to the asymmetric centers. Therefore, lycopadiene (45) was identified as... 

It results from oxidative cleavage of - oleic acid and is produced in commercial quantities mainly by ->ozonolysis (2% ozone in a stream of oxygen - pelargonic acid as a diluent 25-40°C ozonides... 

This cleavage reaction is more often seen in structural analysis than in synthesis The substitution pattern around a dou ble bond is revealed by identifying the carbonyl containing compounds that make up the product Hydrolysis of the ozonide intermediate in the presence of zinc (reductive workup) permits aide hyde products to be isolated without further oxidation... 

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