Dimethylhydrazones, oxidative cleavage

Efficient cleavage of A.A-dimethylhydrazones to yield the parent ketones (>90%) is effected under neutral conditions with tetra-n-butylammonium persulphate [40], The procedure is particularly useful for compounds with acid-sensitive substituents, e.g. vinyl or ketal groups. Similarly, reaction times for the oxidative cleavage of semicarbazones with sodium nitrite or nitrate/trimethylsilyl chloride are reduced by the addition of benzyltriethylammonium chloride [41]. 

Stable nitronium (N02+) salts, particularly with PFfi and Bl, counterions, can act as mild, selective oxidative cleavage reagents for a wide variety of functional groups.497 99 Examples such as the oxidation of methyl ethers [Eq. (5.187)], oximes [Eq. (5.188)], dimethylhydrazones [Eq. (5.189)], and thioacetals [Eq. (5.190)] illustrate the utility of these methods. 

Oxidative cleavage of N,N-dimethylhydrazones. m-Chloroperbenzoic acid is as efficient and more economical than NalOi (7, 126) for cleavage of these hydrazones. The cleavage of the hydrazone 1 was effected without epimerization of the axial methyl group. 

Functional group transformations. Dimethyldioxirane effects conversion of isothiocyanates to isocyanates," TV, Al-dimethylhydrazones of aldehydes to nitriles, and the oxidative cleavage of nitronate ions (Nef reaction) with relative ease. Regioselective oxidation of diols and triols is also achieved. " ... 

Oxidative cleavage of N,N-dimethylhydrazones. This reaction can be conducted by photosensitized oxygenation followed by reduction (dimethyl sulfide) and hydrolysis. Yields of carhonyl compounds are in the range 50-85%. The mechanism is considered to involve an ene-type reaction (equation I). ... 

Oxidative cleavage. N,N-Dimethylhydrazones have been used only to a limited extent as derivatives of carbonyl compounds because oxidative cleavage is sometimes unsatisfactory. This reaction can be accomplished in high yield with aqueous sodium periodate in methanol or THF at pH 7 at 20-25°. Hydrolysis can also be effected in high yield under even milder conditions with copperfll) acetate or chloride (2 equiv.) in aqueous THF. ... 

Oxidative cleavage of hydrazones. Dimethylhydrazones and tosylhydrazones are reductively cleaved to carbonyl compounds by either M0OCI3 or MoFo. Yields are generally in the range of 70-90%. Cf. Tungsten hexafluoride, this volume. 

Oxidative cleavage of hydrazones. This salt converts dimethylhydrazones or tosylhydrazones into the carbonyl compound under mild condilions (CHCla or Freon 113, 75-95% yield).i... 

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