Nitrogen oxygen bond

Decarboxylation of isoxazole-3-carboxylic acids is related to the nucleophilic cleavage of the isoxazole ring as far as the nature of the reaction products is concerned. It occurs at temperatures above 200°C and is accompanied by the cleavage of the nitrogen-oxygen bond of the heterocyclic ring to yield a j8-ketonitrile. It was first reported by Claisen with 5-methyl- and 5-phenyl-isoxazole-3-carboxylic acids (153- 154).Under the reaction conditions, j8-ketonitriles condense... 

The reduction of isoxazoles is often rather peculiar and its course depends on the nature both of the isoxazole and of the reducing agent. Together with a normal reduction of groupings in the side chain, cleavage of the nitrogen-oxygen bond of the heterocyclic nucleus often occurs. 

Shaw concluded that hydrogenation of 3-alkyl-4-aminomethylene isoxazol-5-ones (184) in the presence of palladium catalyst resulted in the saturation of either the endocyclic double carbon-nitrogen bond or the exocyclic double C—C bond with the retention of the heterocyclic nitrogen-oxygen bond. Recent data reported by Kochetkov et al. on the properties, and in particular on hydrogenation, of isoxazolid-5-ones - indicate, however, that Shaw had probably ob-... 

Catalytic cleavage of the nitrogen-oxygen bond occurs very frequently as in reduction of nitro compounds, oximes, and various heterocyclics these reactions are discussed in separate chapters. Considered here are N-oxides, hydroxylamincs, and N- and C-nitroso compounds. 

Amino alcohols are also good substrates for aziridination under Mitsunobu conditions. The rfs-1,4-amino alcohols 48, obtained by reductive cleavage of the nitrogen-oxygen bonds of the hetero Diels-Alder adducts 47, underwent syn-SN2 -type displacement on treatment with PPh3 and DEAD to give cyclic vinylaziridines 49 (Scheme 2.15) [27]. 

It is essential to realize that electrons In the nitrate anion do not flip back and forth among the three bonds, as implied by separate structures. The true character of the anion is a blend of the three, In which all three nitrogen-oxygen bonds are equivalent. The need to show several equivalent structures for such species reflects the fact that Lewis structures are approximate representations. They reveal much about how electrons are distributed in a molecule or ion, but they are imperfect instruments that cannot describe the entire story of chemical bonding, hi Chapter 10, we show how to interpret these structures from a more detailed bonding perspective. 

Experimental studies support our conclusion about the resonance structures of NNO. As we describe in Section 9-1. double bonds are shorter than single bonds. The length of the nitrogen-oxygen bond in NNO is less than typical N—O single bonds but greater than typical NDO double bonds. 

Both benzyl-oxygen and nitrogen-oxygen bonds undergo hydrogenolysis readily in the presence of a benzyloxy-nitrogen bond but it appears that the benzyl-oxygen bond can be made to cleave selec-... 

The nitrogen-oxygen bond is usually cleaved readily by catalytic hydrogenolysis and the reaction has wide synthetic utility. 

Photolysis of the nitric esters 80-82 causes nitrogen-oxygen bond-... 

Nitrogen-Oxygen Bond Formation The anodic oxidation of vicinal dioximes gives 3,4-diphenylfurazan-2-oxide by intramolecular ring formation (Scheme 42) [59]. 

Formation of the Nitrogen-Oxygen Bond 3.5.1 Oxidation of Vicinal Dioximes... 

It has been suggested that a symmetrical intermediate or transition state as represented in Scheme IV.54 could be involved, in which the new and the old nitrogen-oxygen bonds are formed and broken to the same extent. A semiempirical approach for calculating the free energy of activation for the degenerate rearrangement of the anion of 3-acetylamino-5-methyl-l,2,4-... 

Pre-treatment of the cathode produces a finely divided copper surface and this catalyses the hydrogenolysis of phenylhydroxylamine to aniline which becomes the principal reaction product. The reaction probably involves promotion of nitrogen-oxygen bond cleavage in the chemisorbed phenylhydroxylamine intermediate. 

Nitrobenzenes with an ortho or a para hydroxyl or amino function form an exceptional group of compounds in which the nitro function can readily be reduced to amino in alkaline solution. Heterolytic cleavage of the nitrogen-oxygen bond in the phenylliydroxylamine intermediate is promoted by any 2- or 4-substituent which can donate a lone pair of electrons. Further reduction steps then lead to the overall... 

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