Pyridine /V-oxide

Hexamethyldisilazane, Pyridine /V-oxide See Pyridine A-oxide Hexamethyldisilazane, etc. 

It effectively hydroxylates hydrocarbons but is free of the explosion risk of the analogous pyridine /V-oxide complex. 

Further efficient ligands for the epoxidation of alkenes have been reported by Pozzi, but using PhIO as the oxidant and pyridine V-oxide as an additive in FBS.[7, 51-53] Chiral (salen)Mn complexes have been synthesised, which are soluble in fluorous solvents and active in the epoxidation of a variety of alkenes. The catalysts were of the form shown in Figure 6.14. 

In addition to these systematic studies of lanthanide sulfoxide complexes, with variation in both sulfoxide and anion, other more isolated reports are available. Lanthanide isothiocyanate complexes of the cyclic sulfoxides thioxane oxide (490) and tetramethylene sulfoxide (493) have been synthesized and complexes of the unusual potentially chelating ligand 2-(ethylsulfinyl)pyridine-V-oxide (63) described. Detailed studies of the solvation of lanthanide-shift reagents by Me2SO have also appeared (178,179). 

In the pyridine V-oxide series a C-N exchange rearrangement was also observed when 3-aminocarbonyl-l-methoxypyridinium salt (131) reacts with ammonia or alkali, 3-methoxyiminomethylpyridin-2(l//)-one (132) being obtained (74T4055). This conversion takes place via the ANRORC pathway the ring opening occurs between N-1 and C-6 after initial addition of the hydroxide ion at C-6 (Scheme IV.50). 

Very interesting results concerning the cytotoxicity of alkaloids isolated from the flowers of ornamental legume plant Senna spectabilis have been noted by Sriphong et al. . N,0-diacetylcassine, 3(f )-benzoyloxy-2(f )-methyl-6(f )-(lh-oxododecyl)-piperidine and 5-hydroxy-2-methyl-6-(lh-oxododecyl)-pyridine V-oxide exhibited cytotoxicity against KB cell lines. 

N-Oxides are normally resistant to hydroxide attack. However, acetic anhydride converts the N-oxide group into iV-acetoxy cations, and such compounds can be attacked by acetate anions. Thus, the reaction of acetic anhydride with pyridine /V-oxide gives 2-pyridone (Scheme 17). This is a very... 

Pyridine /V-oxides in the presence of acyl halides react with enamines and indoles as shown (Scheme 28). 

Examples treated in this book are summarized in Table 9. One frequently found type consists of ring expansions of cyclic conjugated systems with an exocyclic ylide function, such as pyridine /V-oxides or /V-imides incorporation of the exocyclic half of the ylide function expands the ring by one member. 

Abbreviations 4-pic, 4-methylpyridine PNO, pyridine /V-oxide pip, piperidine PhjAsO, triphenylarsine oxide DPM, 2,2,6,6-tetramethylheptane-3,5-dione. 

The number in parentheses stands for the face selectivity. Face selectivity = % ee, rms x %trans + %ecCII x %cis (reference 44). Reaction was carried out in the presence of 4-(/V,/V-dimethylamino)pyridine /V-oxide. fcThe allylic alcohol was oxidized to the corresponding aldehyde. 

C data are available on several ligands. In Tables 2.3 and 2.4 the relative 13C hyperfine shifts of pyridine and pyridine-/V-oxide are reported [22,37]. In both cases it appears that there is alternation in the shifts, which would indicate n spin delocalization. However, the ratio between the shifts of protons and carbons at each position are different one from the other, and differ from what would be expected on the basis of a simple spin polarization mechanism. It is concluded that more than one mechanism is operative. 

In the pyridinc-A-oxide anion radical, the greatest term of the LUMO belongs to the carbon atom in position 2 (Chaha 1986). In accordance with that, a reaction between the pyridine-.V-oxide anion radical and the benzophenone metal-ketyl yielded preferentially 2-diarylcarbinole derivatives (Kurbatova et al. 1980 Turaeva et al. 1993), Scheme 3-6. 

Separation of five compounds (DL, 6-OH-DL, 3-OH-DL, 7V-OH-DL, and 1-pyridine-/V-oxide-DL) was achieved using an Alliance HPLC system (Waters Corp., Milford, CA) equipped with a 2690 model pump, an autoinjector, a Polaris Cl8-A guard column (Varian Inc., Lake Forest, CA), and a Luna Phenyl-Hexyl analytical column (Phenomenex, Inc., Torrance, CA) maintained at 40°C. For robust characterization of each isomeric compound, an online HDX LC-MS method was developed. The composition of regular and deuterated mobile phases is summarized below ... 

To demonstrate that the proposed methods are suitable for structural elucidation of isomeric metabolites and derivatives in biological matrices, human plasma was spiked with the mixture of DL, 6-OH-DL, 3-OH-DL, /V-OH-DL, and 1-pyridine-/V-oxide-DL. The resulting sample was extracted and analyzed by LC-MS and LC-MS/MS in ESI and APCI modes as described above. HDX was successfully performed online when the extract was injected directly onto the HPLC column without drying and reconstituting the sample in a deuterated solvent. In general, there were no differences between the results obtained for the spiked plasma extract and for the mixture of the standard compounds, which indicates that the LC-MS methods with HDX described here are applicable for the analysis drug-derived material in plasma or other biological matrices. 

Slow addition of hexamethyldisilane in THF to pyridine /V-oxide and tetrabutylammonium fluoride in THF effected smooth reduction to pyridine, while addition of undiluted fluoride led to an explosion on two occasions. 

Oxiranemethanol nitrate, see 2,3-Epoxypropyl nitrate, 1182 Oxiranemethanol, see 2,3-Epoxypropanol, 1225 Oxoacetic acid, see Glyoxylic acid, 0720 Oxobis[aqua(oxo)diperoxorheniumVII], 4532 /(-Oxo-/,/-bis(trifhioroacetato-<9)-/,/-diphenyldiodine(III), 3691 Oxodiperoxodipiperidinechromium(VI), 3361 Oxodiperoxodipyridinechromium(VI), 3268 Oxodiperoxodi(pyridine /V-ox ide)mol ybdenu m, 3273 Oxodiperoxodi(pyridine /V-oxide)tungsten, 3277 Oxodiperoxodiquinolinechromium( VI), 3742 Oxodiperoxomolybdenum—hexamethylphosphoramide, 4713 Oxodiperoxopyridinechromium V-oxide, 1838... 

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