Nitrogen-Containing Substituents

In intramolecular N-coupling the diazonio group interacts with a nitrogen-containing substituent in the ortho-position of the aromatic ring. This is the cause of the difficulties in the diazotization and bisdiazotization of 1,2-diaminobenzene (6.45,... 

TERTIARY PHOSPfflNE LIGANDS WITH NITROGEN-CONTAINING SUBSTITUENTS... 

Although it has become obvious that a fluorine atom in position 6 is the best substituent for antimicrobial activity, the reasons for this effect remain unclear. A comparative study of numerous quinolones seems to indicate that this F-substitution in position 6 affords both a better affinity with gyrase (2-17 times) and the best cell penetration (1-70 times).The presence of this fluorine lowers the basicity of the nitrogen-containing substituent in position 7, and this fact could play a role. However, there are multiple factors to take into account and interpretations must be carefully considered. Thus, replacing the fluorine atom by a chlorine in pefloxacin does not affect the activity on the enzyme, but a decrease of the bacterial activity is observed. This shows the importance of the pharmacokinetic factors. ... 

Various addition reactions to the C = C bond have been studied by Barton and co-workers in the steroid series. Although the yields of products generally depend on the substituent, they are usually higher with oxygen-containing substituents, e.g. 17 (Y = OAc. OMe)34 and 18, and lower with nitrogen-containing substituents, e.g. 17 (Y = pyrrolidino).34" 37... 

Functionalized cyclotrisilane derivatives bearing oxygen- or nitrogen-containing substituents are also known. The synthesis of the aryl-alkoxy cyclotrisilane trimesityl-tris(2,6-diisopropylphenoxy)cyclotrisilane can be easily accomplished by the photolysis of 2-mesityl-2-(2,6-diisopropylphenoxy)-l,l,l,3,3,3-hexamethyltrisilane via several silylene extrusion and addition steps (equation 7)40. 

The following examples illustrate the displacement of halogen by oxygen-, sulfur-, or nitrogen-containing substituents and the exchange of halogen ... 

Gini, G., Lorenzini, M., Benfenati, E., Grasso, P., and Bruschi, M., Predictive carcinogenicity a model for aromatic compounds, with nitrogen-containing substituents, based on molecular descriptors using artificial neural network, J. Chem. Inf. Comput. Sci., 39, 1076-1080, 1999. 

However, Glaxo moved one step further by showing that the imidazole ring could be replaced with a furan ring bearing a nitrogen-containing substituent. This led to the introduction of ranitidine (Zantac) (Fig. 13.56). 

Tautomerism involving phenols is most often seen for Schiff bases, Mannich bases, or o-hydroxyazo aromatics, but is also discussed for o-hydroxynitroso compounds. This is relatively seldom for phenols not having a nitrogen-containing substituent. An exception is 30 and other cases mentioned later. 

Synthesis of a hexopyranoside from a pentofuranoside in the way just described constitutes a chain elongation from within, concomitant with introduction of a nitrogen-containing substituent. This principle57 has been successfully applied in the chemical modification of nucleosides. Pursuant to preliminary reports on such modifications by Fox70 and Lichtenthaler71 and their associates, a considerable body of detailed work in that direction has appeared.72-80... 

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