Other N-Oxidations

Recently, an application of this type of oxidation reaction towards the synthesis of 2-halopyridine N-oxide derivatives, which are intermediates of pyrithione antimicrobial agents, has been patented by a Korean company [146]. It is reported that iron (III) oxide (10-100 mol%) provides the best results among all iron catalysts tested, such as FeCl3, Fe2(S04)3 and Fe(C104)3. 

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Analogous to other N-oxides of polynitrogen heterocyclic bases, quinoxaline 1-oxide and phenazine 9-oxides undergo quater-... 

R = Ar,R2 = H), which were deoxygenated in one instance.19 Other N-oxides (133 R1 = Ar,R2 = H and R1 = R2 = Ph) were obtained directly by hydrazinolysis of the 4-chloropyridine 131b.126 Reaction of hydrazine with the pyridinium salt 134 caused replacement of the methoxy group with formation of 135 29 and, more unexpectedly, 3-carbethoxy-4-pyrrolylpyridine (136) and hydrazine afforded an almost quantitative yield of 137 by expulsion of the pyrrole nucleus.130... 

Finally, the LDA deprotonation of amine N-oxides has been reported to generate azomethine ylides that can be trapped in [2 + 3] cycloadditions with simple alkenes.126 For example, N-methylpyrrolidine N-oxide (137) reacts with LDA in the presence of cyclopentene to give adduct (139 Scheme 31). A variety of other N-oxides behave similarly. Interestingly, there are no examples published to date where nonstabilized azomethine ylides generated by the desilylation procedure can be trapped by simple, unactivated alkenes. It is not clear whether these discrepancies are due to some fundamental difference in the reactive intermediate being generated, or whether the differences in environment are responsible for differing behavior. Further work is needed to establish this point. 

See Other N-OXIDES, TETRAZOLES See related METAL AZOTETRAZOLIDES... 

See 3-Chloroperoxybenzoic acid 2-Bromo-4-methylpyridine See other N-OXIDES... 

Other N-oxidized substrates include mianserin and clozapine both catalyzed by CYP1A2 and CYP3A4. Because the products are identical to those produced by flavin monooxygenases (FMOs), enzymatic studies are required to identify which enzyme system is active during in vivo metabolism. 

It is explosive and a super-electrophile, like 4.6-dinitrobenofurazan -oxide. See other N-OXIDES, POLYNITROARYL COMPOUNDS, TRIAZOLES... 

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