Oximes, oxidative cleavage

Titanium silicate molecular sieves not only catalyze the oxidation of C=C double bonds but can be successfully employed for the oxidative cleavage of carbon-nitrogen double bonds as well. Tosylhydrazones and imines are oxidized to their corresponding carbonyl compounds (243) (Scheme 19). Similarly, oximes can be cleaved to their corresponding carbonyl compounds (165). The conversion of cyclic dienes into hydroxyl ketones or lactones is a novel reaction reported by Kumar et al. (165) (Scheme 20). Thus, when cyclopentadienes, 1,3-cyclohexadiene, or furan is treated with aqueous H202 in acetone at reflux temperatures for 6 h in the presence of TS-1, the corresponding hydroxyl ketone or lactone is obtained in moderate to good yields (208). 

Jousserandot, A., Boucher, J. L., Henry, Y., Niklaus, B., Clement, B., Mansuy, D., Microsomal cytochrome P450 dependent oxidation of N-hydroxyguanidines, amidoximes, and ket oximes mechanism of the oxidative cleavage of their C=N(OH) bond with formation of nitrogen oxides, Biochemistry 37 (1998),... 

Oxidative cleavage of amines 9-39 Reduction of amides 9-47 Reduction of nitro compounds 9-50 Reduction of nitroso compounds or hydroxylamincs 9-51 Reduction of oximes 9-52 Reduction of azides 9-53 Reduction of isocyanates, isothiocyanates, or N-nitroso compounds 9-55 Reduction of amine oxides 9-59 Reduction of azo, azoxy, or hydrazo compounds... 

Strategies that lead to the formation of isoxazoles during cleavage from an insoluble support include the oxidative cleavage of /V-(4-alkoxybenzyl)isoxazolidincs with DDQ to yield isoxazolines (Entry 14, Table 15.16), the nucleophilic cleavage of 2-acyl enamines with hydroxylamine (Entry 15, Table 15.16), and the acidolysis of 2-cyano-phenols etherified with an oxime resin (Entry 17, Table 15.16). The required oxime ethers for the latter synthesis were prepared by reaction of the corresponding 2-fluorobenzonitriles with Kaiser oxime resin [203],... 

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 oximes.2 PDC is recommended for regeneration of ketones and aromatic aldehydes from the oximes (80-100% conversion). The rate of deoximation is increased by addition of 3A molecular sieves, but the yield of the carbonyl compound is lowered. 

In an anionic approach, the sodium salt of the chiral chloroallyl phosphonamide 659 engages in nucleophilic addition onto oximes and gives the optically pure A -alkoxy aziridines 661 (Scheme 161). The chiral auxiliary can be removed by oxidative cleavage of the double bond with ozone <2000TL787>. 

Cyclopropanation of the cinnamate 52 followed by oximinatlon gave rac-53. Asymmetric reduction of the oxime ether gave two diastereomers, one of which was taken on to 54 by oxidative cleavage of the furyl group. 

A -Bromosaccharin 217 is an efficient reagent for the oxidative cleavage of oxime 216 to the corresponding aldehydes and ketones 218 under microwave irradiation <04S1739>. The hydroxyl functional group is well tolerated under these conditions. 

Deprotection. Removal of the 2-naphthylmethyl group from 2-NpCH20R and oxidative cleavage of oximes and tosylhydrazones with DDQ proceed under mild conditions. Smooth and selective transformation of RNBn2 to RNHBn at room temperature by DDQ in dichloromethane containing some water is observed. ... 

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