Reduction N-oxides

IV. The Chemical Mechanism of Pyridine N-oxide Reduction A. The Initial Step... 

For purposes of pyridine N-oxide reduction, it suffices to say that many examples of Eq. (14) have been explored, including those in which PR3 is displaced contra-thermodynamically (p/TM may be ca. 2) by PyO. Invoking such a step in the catalytic cycle is therefore perfectly acceptable. Actually, the ligand displacement chemistry is a rich and fascinating area in its own right, and for that reason it will be explored independently in Section V. 

Oxidation of heterocyclic aromatic amines, N-oxide reduction... 

The fact that the cytochrome P-450 was induced even in the presence of NH3, which is the end product of assimilatory N-oxide reductions, suggested that it might funciton in dissimilatory N-oxide reductions. Anaerobic growth experiments with induced cells showed that reduction of nitrate to nitrite was energy yielding in F. oxysporum but reduction of nitrite to N2O was probably not (Shoun and Tanimoto, 1991). 

Deoxygenation of N-oxides reduction of ArNO2. An Mo(IIl) species obtained by reduction of MoC15 with zinc in aqueous THF reduces aromatic N-oxides in 45 65% yield. The reagent also reduces aromatic and heteroaromatic nitro compounds lo amines in 30-70% yield. 

Microderivatization or chemical modification of analytical samples can be useful in enhancing the ion response, and hence the LC-MS sensitivity, for any particular analyte. In the case of alkaloids, which are already capable of ready ionization, chemical modification can be more valuable in elucidating structures by providing tandem MS evidence for positions of substitution in the parent molecule. Such derivatization or chemical modification for HPLC-MS can include H/D exchange by using deuterated mobile phases, Jones oxidation of aliphatic hydroxyls, selective acetylation of hydroxyl and amine groups, and N-oxide reduction [19,20]. 

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