Olefin ozonolysis

The C-Si bond of an SMA can also be cleaved by oxidizing reagents like cerium ammonium nitrate (CAN). Starting from (V-bis(trimethylsilyl)methylazetidinones, treatment with CAN probably leads to the oxidation product of the two C-Si bonds, i.e., the corresponding disilylketal that is hydrolyzed into the formamide to give the N-H azetidinones (yields >80%). This constitutes an alternate and more efficient way to sequential fluoride-induced desilylation. Peterson olefination, ozonolysis, and formamide decomposition when deprotection of bis(trimethylsilyl)methylated azetidinones into NH-azetidinones is required.228,230... 

The nature and the distribution (Table II) of the ozonolysis products in conjunction with the probable modes of their formation allow also a qualitative rationalization of the observed ozone-olefin stoichiometry. Three reactions compete with ozone for the starting material, trans-2,3-dibromo-2-butene. These reactions are the formation of 3,3-dibromobutanone, 31, and the formation of the brominated products, 34 and 35. On the other hand, hydrogen bromide is oxidized to form bromine and water, which consumes ozone on top of the regular olefin— ozonolysis reaction. An attempt to explain the observed stoichiometry quantitatively did, however, not lead to a satisfactory correlation between the actual ozone consumption and the observed material balance. This... 

The direct conversion of olefins into esters is accomplished during mono-, di- and thi-substituted olefins ozonolysis in 2.5 M methanol sodium hydroxide-dichloromethane solution. The methyl esters are obtained in high yields. Thus, 3-benzyloxy-l-nonene (5b) is transformed into 2-benzyloxyoctanoate (7b) in 78% 5deld [84],... 

Nickel(O) forms a n-complex with three butadiene molecules at low temperature. This complex rearranges spontaneously at 0 °C to afford a bisallylic system, from which a large number of interesting olefins can be obtained. The scheme given below and the example of the synthesis of the odorous compound muscone (R. Baker, 1972, 1974 A.P. Kozikowski, 1976) indicate the variability of such rearrangements (P. Heimbach, 1970). Nowadays many rather complicated cycloolefins are synthesized on a large scale by such reactions and should be kept in mind as possible starting materials, e.g. after ozonolysis. 

Versatile [3 + 2]-cydoaddition pathways to five-membered carbocydes involve the trimethylenemethane (= 2-methylene-propanediyl) synthon (B.M. Trost, 1986). Palladium(0)-induced 1,3-elimination at suitable reagents generates a reactive n -2-methylene-l,3-propa-nediyl complex which reacts highly diastereoselectively with electron-deficient olefins. The resulting methylenecyclopentanes are easily modified, e. g., by ozonolysis, hydroboration etc., and thus a large variety of interesting cyclopcntane derivatives is accessible. 

The early Escherunoser-Stork results indicated, that stereoselective cyclizations may be achieved, if monocyclic olefins with 1,5-polyene side chains are used as substrates in acid treatment. This assumption has now been justified by many syntheses of polycyclic systems. A typical example synthesis is given with the last reaction. The cyclization of a trideca-3,7-dien-11-ynyl cyclopentenol leads in 70% yield to a 17-acetyl A-norsteroid with correct stereochemistry at all ring junctions. Ozonolysis of ring A and aldol condensation gave dl-progesterone (M.B. Gravestock, 1978 see p. 279f.). 

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... 

By-products include ozonides (17). Other peroxidic products including polymeric peroxides and polymeric ozonides can form, depending on reaction conditions, solvent, and olefin used. A variety of cycHc diperoxides (4) have been obtained by ozonolysis of olefins. Both cis- and... 

Rhodium catalyst is used to convert linear alpha-olefins to heptanoic and pelargonic acids (see Carboxylic acids, manufacture). These acids can also be made from the ozonolysis of oleic acid, as done by the Henkel Corp. Emery Group, or by steam cracking methyl ricinoleate, a by-product of the manufacture of nylon-11, an Atochem process in France (4). Neoacids are derived from isobutylene and nonene (4) (see Carboxylic acids, trialkylacetic acids). 

Examples are given of common operations such as absorption of ammonia to make fertihzers and of carbon dioxide to make soda ash. Also of recoveiy of phosphine from offgases of phosphorous plants recoveiy of HE oxidation, halogenation, and hydrogenation of various organics hydration of olefins to alcohols oxo reaction for higher aldehydes and alcohols ozonolysis of oleic acid absorption of carbon monoxide to make sodium formate alkylation of acetic acid with isobutylene to make teti-h ty acetate, absorption of olefins to make various products HCl and HBr plus higher alcohols to make alkyl hahdes and so on. 

While the reductive procedure appears simpler, it also provides a higher proportion of the A -double bond isomer on dehydration than is obtained from the tertiary carbinol. This may be a consequence of the lower steric requirements of a A -olefin having only one alkyl group attached to C-20. In either case, all other double bonds must be protected before the ozonolysis and other free hydroxyls should be esterified prior to dehydration at C-20. 

A well-known example for a 1,3-dipolar compound is ozone. The reaction of ozone with an olefin is a 1,3-dipolar cycloaddition (see ozonolysis). 

Since double bonds may be considered as masked carbonyl, carboxyl or hydroxymethylene groups, depending on whether oxidative or reductive methods are applied after cleavage of the double bond, the addition products from (E)-2 and carbonyl compounds can be further transformed into a variety of chiral compounds. Thus, performing a second bromine/lithium exchange on compound 4, and subsequent protonation, afforded the olefin 5. Ozonolysis followed by reduction with lithium aluminum hydride gave (S)-l-phenyl-l,2-ethanediol in >98% ee. 

Johnson has developed two linear approaches to synthesize the C-nor-D-homosteroid skeleton (Scheme 2.2). In his first approach [21], tetralone 19, obtained from reduction of 2,5-dimethoxynaphthalene, was used as the source of the C,D-rings. The B- and A-rings were constructed by sequential Robinson annulations (19 —> 20 —> 21). The Cl 1,12 olefin was then introduced to provide 22. Ozonolysis of 22 followed by an aldol reaction of the resulting dialdehyde gave 23. Subsequent deformylation and deoxygenation afforded the cyclopamine skeleton 24. 

In contrast to the Johnson s D —> A-ring construction approach, Brown devised an A —> D-ring construction approach [22]. Starting from Wieland-Miescher ketone (30), a common source of the A, B-rings in the de novo synthesis of steroids, the C-ring was introduced via hydrazone allylation, ozonolysis, aldol condensation, and olefin isomerization (31 > 32). The D-ring was assembled by a reductive alkylation... 

Other oxidation chains can be constructed. For example, when methyl radicals are generated by other reactions, as in the ozonolysis of olefins, the following reactions can occur ... 

Fliszar, S., and J. Renard. Quantitative investigation of the ozonolysis reaction. XIV. A simple carbonium ion stabilization approach to the ozone cleavage of un-symmetrical olefins. Can. J. Chem. 48 3002-3018, 1970. 

Olefins. 57-58 as source of ozone, 26 cyclic, 4, 60. 70-72, 675 effect of singlet oxygen on, 33 ozonolysis, 22... 

The ozonolysis reaction, followed by reductive workup with sulfur dioxide, as described in Part A of the present procedure, illustrates a general method which has been developed for the preparation of acetals. Application of the procedure is illustrated by conversion of the following olefins in alcoholic solution to the corresponding acetals (1) l-chloro-4-(o-nitrophenyl)-2-butene to o-nitrophenylacetaldehyde dimethyl acetal in 84% yield (2) l,4-dibromo-2-butene tobromoacetaldehyde dimethyl acetal in 67% yield (3) 3-butenoic acid to malonaldehydic acid diethyl acetal ethyl ester in 61% yield (4) cyclopentadiene to malonaldehyde bis(diethyl acetal) in 48% yield and (5)... 

The ozonolysis of olefins has been studied for over 60 years, and is stiU the subject of current research. The principle interest lies in the complex mechanism of dipolar additions, chain scissions, and recombinations that are the source of the complexity... 

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