Replacement, nitro group

A Similar, but probably nucleophilic substitution was studied by Lobry de Slum and van Leent [134]. By acting with hydrocliloride at 250°C they replaced nitro groups in dinitrobenzenes and s-trinitrobenzene to obtain dichloro-iien/enes and s-trichlorobcnzene respectively. 

The nitrochlorobenzenes are valuable dyestufTs intermediates. The presence of the nitro-groups makes the chlorine atom very reactive and easily replaceable. Treatment with ammonia or dilute alkalis substitutes an amino- or hydroxy-group for the chlorine atom and gives a series of nilroanilines and nilrophenols. 

Nitromethane, CH3NO2, the first member of the homologous series, can, however, be readily prepared by a special reaction. When equimolecular amounts of sodium nitrite and sodium monochloroacetate are heated together in aqueous solution, the chlorine in the monochloroacetate is replaced by the nitro group, and the sodium nitroacetate thus formed undergoes hydrolysis follow ed by decarboxylation ... 

Nitration Warming benzene with a mixture of nitric acid and sulfuric acid gives nitrobenzene A nitro group (—NO2) replaces one of the ring hydrogens... 

In the examples, a nitro group is substituted for a hydrogen atom, and water is a by-product. Nitro groups may, however, be substituted for other atoms or groups of atoms. In Victor Meyer reactions which use silver nitrite, the nitro group replaces a hahde atom, eg, I or Br. In a modification of this method, sodium nitrite dissolved in dimethyl formamide or other suitable solvent is used instead of silver nitrite (1). Nitro compounds can also be produced by addition reactions, eg, the reaction of nitric acid or nitrogen dioxide with unsaturated compounds such as olefins or acetylenes. 

Nitroparaffias (or nitroaLkanes) are derivatives of the alkanes ia which one hydrogen or more is replaced by the electronegative nitro group, which is attached to carbon through nitrogen. The nitroparaffins are isomeric with alkyl nitrites, RONO, which are esters of nitrous acid. The nitro group ia a nitroparaffin has been shown to be symmetrical about the R—N bond axis, and may be represented as a resonance hybrid ... 

In the first synthesis of T, the diphenyl ether was formed from -methoxyphenol and 3,4,5-triiodonitrobenzene. The nitro group was replaced by a nitril which was then built up into the alanyl side chain by a series of steps (10). 

The ring-chlorinated derivatives of toluene form a group of stable, industrially important compounds. Many chlorotoluene isomers can be prepared by direct chlorination. Other chlorotoluenes are prepared by indirect routes involving the replacement of amino, hydroxyl, chlorosulfonyl, and nitro groups by chlorine and the use of substituents, such as nitro, amino, and sulfonic acid, to orient substitution followed by their removal from the ring. 

Alkoxyl tion. The nucleophilic replacement of an aromatic halogen atom by an alkoxy group is an important process, especially for production of methoxy-containing iatermediates. Alkoxylation is preferred to alkylation of the phenol wherever possible, and typically iavolves the iateraction of a chloro compound, activated by a nitro group, with the appropriate alcohol ia the presence of alkaU. Careful control of alkaU concentration and temperature are essential, and formation of by-product azoxy compounds is avoided by passiag air through the reaction mixture (21). 

Cl Vat Red 10 is prepared by condensation of l-nitroanthraquinone-2-carboxyhc acid chloride with 2-amino-3-hydroxyanthraquinone followed by ring closure in sulfuric acid and subsequent replacement of the nitro group with aqueous ammonia. 

The second most important nucleophilic substitution in pyridazine A-oxides is the replacement of a nitro group. Nitro groups at the 3-, 4-, 5- and 6-position are easily substituted thermally with a chlorine or bromine atom, using acetyl chloride or hydrobromic acid respectively. Phosphorus oxychloride and benzoyl chloride are used less frequently for this purpose. Nitro groups in nitropyridazine A-oxides are easily replaced by alkoxide. The... 

Amino groups are formed by reduction of nitro groups in aryl substituents and behave normally (62JCS1671), but when attached directly to the pyridopyridazine ring they may be removed by acid hydrolysis or treatment with nitrous acid, or replaced by hydrazine. 

The analogous reactions of 5-nitro- [227] and 5-bromofuran-2-carboxylic acids [228] lead to addition of two fluorine atoms and replacement of the nitro group... 

Replacement of nitro groups by fluoride ion represents a useful route to organic fluorine compounds... 

A nitro group in the artho or para position to fluonne is known to enhance its replacement by hydroxyl [II, 12] Bromine and iodine are much less prone to hydrolysis under similar conditions The effect is much less pronounced with the meta nitro derivative (equation 11) With o-nitro-p-fluoroaniline, it is the amino group ortho to the nitro group, rather than meia fluorine, that is replaced by hydroxyl (equation 12)... 

POCls-catalyzed formylation, so POBrs must be used instead. Another example is the replacement of halogen by the nitro group in the nitration of halogenated 2-acetamidothiophenes. ... 

Nitro and azido. In benzene derivatives, the nitro group is said to rival fluorine and exceed chlorine in replaceability. The reactivity of the nitro group in heterocycles is also very high, and this... 

A new general synthesis of 3-substituted derivatives has been reported (99MC13) (Scheme 9). Thus, the nitro group of furoxan 27 underwent a facile hydride replacement on treatment with NaBH4 in EtOH to give 3-monosubstituted furoxans 23. The result of this reaction is independent of the nature of R. 

Replacement of chlorine on the pendant benzoyl group by azide is apparently consistent with antiinflammatory activity. Acylation of indomethacin intermediate with p-nitrobenzoyl chloride leads to the corresponding amide (7). Saponification ( ) followed by reduction of the nitro group gives the amine 9. The diazonium salt (10) obtained on treatment with nitrous acid is then reacted with sodium azide there is thus obtained zidomethacin (11). 

Nucleophilic aromatic substitution of the anion from ary lace ton itrile 113 on the dichloroni-trobenzene 114 results in replacement of the para halogen and formation of 115. Reduction of the nitro group gives the corresponding aniline (116). Acylation of the amine with 3,5-diiodoacetylsa-licylic acid 117 by means of the mixed anhydride formed by use of ethyl chloroformate, gives, after alkaline hydroly.sis, the anthelmintic agent closantel (118) [28]. 

The majority of analgesics can be classified as either central or peripheral on the basis of their mode of action. Structural characteristics usually follow the same divisions the former show some relation to the opioids while the latter can be recognized as NSAlD s. The triamino pyridine 17 is an analgesic which does not seem to belong stmcturally to either class. Reaction of substituted pyridine 13 (obtainable from 12 by nitration ) with benzylamine 14 leads to the product from replacement of the methoxyl group (15). The reaction probably proceeds by the addition elimination sequence characteristic of heterocyclic nucleophilic displacements. Reduction of the nitro group with Raney nickel gives triamine 16. Acylation of the product with ethyl chlorofor-mate produces flupirtine (17) [4]. 

Antidepressant activity is retained when the two carbon bridge in imipramine is replaced by a larger, more complex, function. Nucleophilic aromatic substitution on chloropyridine 31 by means of p-aminobenzophenone (32) gives the bicyclic intermediate 33. Reduction of the nitro group (34), followed by intramolecular Schiff base formation gives the required heterocyclic ring system 35. Alkylation of the anion from 35 with l-dimethylamino-3-chloropropane leads to tampramine 36 [8]. 

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