Nitrones dimethyldioxirane

The most widely employed methods for the synthesis of nitrones are the condensation of carbonyl compounds with A-hydroxylamines5 and the oxidation of A+V-di substituted hydroxylamines.5 9 Practical and reliable methods for the oxidation of more easily available secondary amines have become available only recently.10 11 12 13. These include reactions with stoichiometric oxidants not readily available, such as dimethyldioxirane10 or A-phenylsulfonyl-C-phenyloxaziridine,11 and oxidations with hydrogen peroxide catalyzed by Na2W044 12 or Se02.13 All these methods suffer from limitations in scope and substrate tolerance. For example, oxidations with dimethyldioxirane seem to be limited to arylmethanamines and the above mentioned catalytic oxidations have been reported (and we have experienced as well) to give... 

Dimethyldioxirane oxidation of nitronates anions affords the corresponding carbonyl products. Highest yields are obtained when one equivalent of water is added before the oxidation (Eq. 6.9).17... 

Oxidation of A-alkyl imines with dimethyldioxirane (DMD) in a solution of dichloromethane-acetone gives nitrones without the apparent formation of oxaziridines (13). Under the conditions of phase transfer, imines can be oxidized into nitrones upon treatment with permanganate ion MnC>4 (19). 

Polymer-supported permthenate has also been used in two convergent pathways for the synthesis of isoxazoUdines with each route employing different starting materials in order to create the maximum structural diversity [73]. In the first route secondary hydroxylamines, readily prepared from amines by in situ treatment with dimethyldioxirane, were oxidized directly to nitrones using polymer-supported permthenate (PSP). Alternatively, primary alcohols were used as the... 

In a very interesting paper Hu and Miller have described the synthesis of a L-lysine-derived cyclic hydroxamic acid 174 starting by the oxidation of protected Z-L-lysine 171 (formed from 170) with dimethyldioxirane (DMD) in acetone, followed by nitrone... 

Oxidation. Benzylic secondary amines are oxidized in high yield by dimethyldioxirane to nitrones,1 probably via hydroxylamines.2... 

Treatment of 4/f-imidazoles 1549 with dimethyldioxirane resulted in formation of amino-nitrones 1550 regio-selectively (Ar = 4-MeC6H4, 4-MeOC6H4, 4-/-BUC6H4, naphthyl). Compounds 1550 are unusually stable due to contributions from anionic as well as cationic delocalized mesomeric structures (Scheme 400) <2000JPR245>. 

Dimethyldioxirane in wet acetone oxidizes isocyanates to nitro compounds (RNCO —> RN02). Oximes can be oxidized to nitro compounds with peroxytri-fluoroacetic acid, or Oxone , sodium perborate, among other ways. Secondary hydroxylamines are also oxidized to nitrones with Mn02 in dichloromethane. " Primary and secondary alkyl azides have been converted to nitro compounds by treatment with PhsP followed by ozone.Aromatic nitroso compounds are easily oxidized to nitro compounds by many oxidizing agents. OS III, 334 V, 367, 845 VI, 803 81, 204. 

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. " ... 

The inseparable isomeric nitrones formed by reaction of deoxynojirimycin (DNJ) derivative 63 with dimethyldioxirane, gave the 1,3-dipolar cycloadducts 64 and 65 on reaction with trichloroacetonitrile (Scheme 12). The P-l-C-substituted-DNJ derivative 66 was obtained from the reaction of a related nitrone with methyl 3-butenoate under high pressure (15 kbar), but overall the access to this... 

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