Oxidative Cleavage of Olefins

Oxidative cleavage of carbon-carbon double bonds or v/c-diols can lead to aldehydes, ketones or carboxylic acids depending upon the conditions employed. Oxidative cleavage of olefins is important from the viewpoint of 

The oxidation catalyst is believed to be ruthenium tetraoxide based on work by Engle,149 who showed that alkenes could be cleaved with stoichiometric amounts of ruthenium tetraoxide. Suitable solvents for the Ru/peracid systems are water and hexane, the alkene (if liquid) and aromatic compounds. Complex-ing solvents like dimethylformamide, acetonitrile and ethers, and the addition of nitrogen-complexing agents decrease the catalytic system s activity. It has also been found that the system has to be carefully buffered otherwise the yield of the resulting carboxylic acid drops drastically.150 The influence of various ruthenium compounds has also been studied, and generally most simple and complex ruthenium salts are active. The two exceptions are Ru-red and Ru-metal, which are both inferior to the others. Ruthenium to olefin molar ratios as low as 1/20000 will afford excellent cleavage yields ( 70%). vic-Diols are also 

As with percarboxylic acids, hydrogen peroxide usually requires metal activation.151-154 Peroxo complexes of d° transition metals can often be used to cleave olefins. Tungstic acid cleaves olefins to the carboxylic acid using 35% m/m hydrogen peroxide.154 Sodium tungstate has also been reported to 

Substrate Conversion (%) Acid yield (%) Aldehyde yield (%) 

Hydrogen peroxide with Milas reagent is also suitable for the cleavage of olefins. The system has been used to prepare aromatic aldehydes such as anisaldehyde from anethole, pipernal from isosafrole and vanilin from iso-eugenol.170,171 Hydrogen peroxide and chromium(III) can be used to cleave methyl methacrylate to methyl pyruvate.172 

Another possibility is the use of tungsten, which has led to excellent results for the conversion of cyclohexene to adipic acid (see Fig. 4.23) [48]. For linear olefins using the Venturello-system, oxidative cleavage products can be obtained in around 80% yield [96]. 

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Oxidative cleavage of olefins is frequently a useful procedure synthetically as well as analytically. Ozonization is an effective means of carrying out such a cleavage under... 

Oxidative cleavage of olefins, terminal alkynes, or aromatic rings 9-11 Oxidation of aromatic side chains 9-21 Oxidation of amines 9-22 Oxidation of primary alcohols or ethers... 

Homolytic autoxidations of hydrocarbons often give complex mixtures of products-the autoxidation of olefins is a prime example. There is a great incentive, therefore, to search for catalysts that can promote the selective oxidation of olefins by essentially nonradical mechanisms. For example, there is no method available for carrying out the selective epoxidation or oxidative cleavage of olefins (see Section III.C) by molecular oxygen. In order to be successful, any heterolytic pathway for the metal-catalyzed oxidation of a substrate must, of course, be considerably faster than the ubiquitous homolytic processes for autoxidation. Thus, the metal catalysts discussed in the following sections, in addition to being able to promote heterolytic oxidations, are also able to catalyze homolytic processes. 

There is considerable industrial interest in the direct epoxidation or oxidative cleavage of olefins with molecular oxygen by the following overall transformations ... 

Fig. 12 Mechanism of Ru04-mediated oxidative cleavage of olefins...

Fig. 4.34 A catalytic cycle for ruthenium-catalyzed oxidative cleavage of olefins.

The tandem 0s04-catalyzed oxidative cleavage of olefin 269 with Oxone as the co-oxidant and sequential direct oxidation of intermediate aldehyde in alcoholic media led to cyclic keto lactone 270 in 45% yield (Equation 34) <20030L3089>. Similar oxidative cyclization with KMnCT-GuSITr resulted in 32% yield of 270 <1994T11709>. 

The mono-pincer ruthenium(II) complex was successfuUy employed in the oxidative cleavage of olefins to aldehydes, dialdehydes or keto-aldehydes. 

As an oxometal component, osmium tetroxide is the most reliable reagent on the laboratory scale to produce c/s-diols. Ruthenium tetroxide in the presence of NaI04 effects oxidative cleavage of olefins [4], but has been successfully employed for so-called lightning dihydroxylation reactions using a two-phase medium [6]. 

The synthesis of the C29-C51 EF segment 518 started with olefin 508 having three chiral centers, prepared by utilizing crotyl- and allyl-boronate chemistry (Scheme 73). Oxidative cleavage of olefin 508, debenzylation, and dehydration afforded glycol 509, which was converted into iodoglycal 510 by the Freisen method. 

Oxidative cleavage of olefins to aldehydes by the usual oxidants... 

Oxidative cleavage of olefins to ketones and carboxylic acids by the usual... 

From a preparative point of view the commonest use of oxidative cleavage of olefins by the usual oxidizing agents is for preparation of ketones and, even more so, of carboxylic acids. Azelaic acid is obtained by permanganate oxidation of ricinoleic acid as follows 113... 

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 ... 

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