Oxidative Cleavage of Double Bonds

Double bonds are oxidatively cleaved to alcohols, aldehydes, ketones, or acids. The specific product formed depends on the structure of the alkene, that is, the presence or absence of hydrogen atoms at the carbons of the double bonds, and on the oxidants used. 

The oldest and still very common cleavage is the reaction of unsaturated compounds with ozone and the subsequent treatment of the ozonides formed (equations 95 and 96). Reduction by strong reducing agents such as complex hydrides gives alcohols [94. Cycloalkenes yield diols [82]. 

An example showing the different products formed by different reducing agents is the ozonolysis and reduction of 2-phenylskatole (3-methyl-2-phenylindole) (equation 97) [95]. 

A much more frequently used reaction is the cleavage of unsaturated compounds to aldehydes (equations 98 and 99). Alkenes and cycloalkenes that possess one or two hydrogens at the double bonds are oxidized by ozone to ozonides, which have to be reduced to prevent a subsequent oxidation to acids by the excess oxygen atom. Reductions are carried out, usually without isolation of the ozonides, by catalytic hydrogenation over palladium catalyst [80, 81,1106] or Raney nickel [55] or by treatment with 

As alternatives to ozonolysis, other oxidations are used to prepare aldehydes from unsaturated compounds treatment of alkenes with chromyl 

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Osmium tetroxide used in combination with sodium periodate can also effect alkene cleavage.191 Successful oxidative cleavage of double bonds using ruthenium tetroxide and sodium periodate has also been reported.192 In these procedures the osmium or ruthenium can be used in substoichiometric amounts because the periodate reoxidizes the metal to the tetroxide state. Entries 1 to 4 in Scheme 12.18 are examples of these procedures. Entries 5 and 6 show reactions carried out in the course of multistep syntheses. The reaction in Entry 5 followed a 5-exo radical cyclization and served to excise an extraneous carbon. The reaction in Entry 6 followed introduction of the allyl group by enolate alkylation. The aldehyde group in the product was used to introduce an amino group by reductive alkylation (see Section 5.3.1.2). 

Silica gel-based catalytic systems have been described as efficient promoters for a number of organic reactions.28 Illustrative examples include the oxidative cleavage of double bonds catalyzed by silica-supported KM11O4,29 reaction of epoxides with lithium halides to give /i-halohydrins performed on silica gel,30 selective deprotection of terf-butyldimethylsilyl ethers catalyzed by silica gel-supported phosphomolybdic acid (PMA),31 and synthesis of cyclic carbonates from epoxides and carbon dioxide over silica-supported quaternary ammonium salts.32... 

Osmium tetroxide used in combination with sodium periodate can also effect alkene cleavage.135 Successful oxidative cleavage of double bonds using ruthenium tetroxide and sodium periodate has also been reported.136 In these procedures, the osmium or ruthenium can be used in substoichiometric amounts because the periodate reoxidizes the metal to the tetroxide state. Entries 1 4 in Scheme 12.17 are examples of these procedures. 

The strong oxidants Cr(VI) and Mn04 can also be used for oxidative cleavage of double bonds, provided there are no other sensitive groups in the molecule. The permanganate oxidation proceeds first to the diols and ketols, as described earlier (p. 757), and these are then oxidized to carboxylic acids or ketones. Good yields can be obtained provided care is taken to prevent subsequent oxidative degradation of the products. Entries 5 and 6 in Scheme 12.17 are illustrative. 

Oxidative Cleavage of Double Bonds and Aromatic Rings Oxo-de-alkylidene-bisubstitution, etc. 

The mechanism of oxidative cleavage of double bonds is commonly supposed to be the result of coordination of Ru-dioxo species to the double bond... 

Scheme VIII/31. Oxidative cleavage of double bond zero bridge in bicycles [97] [98].

Table 4 The Oxidative Cleavage of Double Bonds to Carbonyl Compounds by Permanganate...

Additional examples of the oxidative cleavage of double bonds permanganate to produce aldehydes and ketones are summarized in Table 4. A detailed stucty of the reaction medianism has also been reported. ... 

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). 

Oxidations of halogenated alkenes to carboxylic acids are discussed in a previous section, Oxidative Cleavage of Double Bonds (equations 118-120). 

Brown s conditions afforded 564 with high ee. Acylation, oxidative cleavage of double bond, and Wittig olefination gave (Z)-vinyl iodide 565. 

Oxidative cleavage of double bonds. The oxidation in water is catalyzed by sand. 

A large body of scientific evidence suggests that the loss of food palatability as a result of lipid oxidation is due to the production of short chain compounds from the decomposition of the hydroperoxides. The volatile compounds produced from the oxidation of edible oils are influenced by the composition of the hydroperoxides and the positions of oxidative cleavage of double bonds in the fatty acids." ... 

The plausible biosynthesis of camptothecin is outlined in Scheme 22.6. Strictosamide 45 may undergo oxidative cleavage of double bond giving diketo derivative 46 which provides pumiloside 47 after intramolecular aldol condensation (similar reaction sequence executed by chemical transformation was reported by Hutchinson [169]). Reduction of quinolone part in 47 afforded 48, which forms CPT after double-bond rearrangement and hydrolytic cleavage of glucose. 

Osmium tetroxide used in combination with sodium periodate can also effect alkene cleavage cleanly.Successful oxidative cleavage of double bonds using ruthenium... 

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