Cleavage, of ketones

Nal, CeCl3 7H20, CH3CN, rt, 0.5-21 h, 84-96% yield. Chemoselective cleavage of ketone derivatives is observed in the presence of aldehyde derivatives, and enone ketals are cleaved in the presence of simple ketone ketals. 

Cleavage of ketones with amide ion (Haller-Bauer)... 

Type I cleavage of ketones, 75 Type II cleavage of ketones effect of 7-substituents, 122-124 effect of ring substituents, 124 of 5 -(+)-4-methyl-l-phenyl-1- hexanone, 118... 

The Gotor group succeeded in using almond meal for the enantioselective cleavage of ketone cyanohydrins, which served additionally as the cyanide source in the subsequent asymmetric addition of HCN to co-bromoaldehydes in one pot (Figure 9.4) [53]. 

Cleavage of ketones with sodium amide is called the Haller-Bauer reaction.514 As with 2-45, which is exactly analogous, the reaction is usually applied only to nonenolizable ketones, most often to ketones of the form ArCOCR3, where the products R3CCONH2 are not easily attainable by other methods. However, many other ketones have been used, though benzophenone is virtually unaffected. It has been shown that the configuration of optically active R is retained.515 The NH2 loses its proton before the R is cleaved 516... 

Oxidative Cleavage of Ketones. Aldehydes, and Alcohols Cycloalkanone oxidative ring opening... 

Fig. 102 Mn(II)-Co(II)-catalyzed oxidative cleavage of ketones to benzoic acids...

The Baeyer-Villiger rearrangement often is called Baeyer-Villiger oxidation (see the last subsection of Section 14.3.2, Oxidative Cleavage of Ketones). In the Baeyer-Villiger rearrangement a carbonyl compound (ketones are almost always used) and an... 

When radical pairs are produced by a cleavage of ketones, and the loss of CO is prevented on energetic grounds, fragments of the reactions of the primary radical pair become important. Deoxybenzoins (15)30) or adamantyl ketones (20)25,30) provide examples of such systems. The photodecomposition of l,2-diphenyl-2-methyl-pro-panone (15)30) illustrates an example of a photofragmentation in reaction (Scheme VIII). The ratio of the major products are highly dependent on solvent environment. For example, the photochemistry of this compound in acetonitrile or benzene yields... 

Oxidative cleavage of ketones. Potassium superoxide in combination with Aliquat 336 oxidizes ketones in benzene solution at 20°. Ketones lacking an cf-hydrogen and 1,3-diketones do not react. 

The McLafferty rearrangements is the mass spectrometric analog of the Norrish type II photochemical cleavage of ketones. The relationship between these two processes is easily the most extensively studied of aU mass spectral photochemical correlations. In addition to the well known reaction of aldehydes, ketones, and esters, Eq. (62), many analogous y-hydrogen... 

Cleavage of ketones by oxidation is infrequently used for preparation of monocarboxylic acids. Trimethylacetic acid is made in 75% yield from pinacolone, (CHj)jCCOCHj, by oxidation with chromic anhydride in aqueous acetic acid. Cleavage on only one side of the carbonyl group is possible in this case. 

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