Nitroanilines diazotization

Dimethylaminocinnamaldehyde Ehrlich reagent Ferric chloride (3%) p-Nitroaniline, diazotized Sodium bisulfite, aqueous Ninhydrin... 

CgHgNa. While crystals m.p. 147 C, b.p. 267"C, darken rapidly in air. Prepared by reducing p-nitroaniline or aminoazobenzene. Oxidizing agents convert it to quinone derivatives, hence it cannot be diazotized with nitric acid. 

Amino-5-methylthiazole does not react with diazotized p-nitroaniline in solutions acidified with acetic or hydrochloric acid (391). 2-Amino-4,5-dimethylthiazole with the diazonium salts of para-substituted anilines, however, gives product 193, involving reactivity of the exocyclic nitrogen (Scheme 122) (399). 

An azo coupling reaction of monatomic phenols with diazotized 4-nitroaniline has been investigated. By HPLC, NMR, elemental analysis, UV and IR spectroscopy it has been shown that the azo derivatives of o-guaiacol, o- and m-cresols interact with an excess of diazonium in pH interval of 4,5-9,5 and form corresponding 4,4-di(4-nitrophenylazo)-2,5-cyclohexadien-1 -ones. 

An azo coupling reaction of primary aromatic and aliphatic amines with diazotized 4-nitroaniline in water-organic solutions has been investigated. It has been demonstrated that depending on the nature of an organic solvent different azo derivatives are formed in neutral medium. 

Diaminoazobenzene was reported by Nietzki to have been prepared by diazotizing -nitroaniline and coupling the product with aniline. The resulting 4-nitrodiazoaminobenzene is rearranged and the nitro group reduced. The submitters tried several times to carry out this procedure but were unsuccessful. 4,4 -Diaminoazobenzene has been prepared by the oxidation of -nitroaniline with potassium persulfate followed by the reduction of the nitro groups. ... 

The NH2 groups can be diazotized and reduced in the presence of thiosulphates and different metal ions. The effect of some metal ions, namely Fe ", Sn, Cu +, and Co on the graft yield of cotton modified with aryl diazonium groups via its reaction with 2,4-dichloro-6-(p-nitroaniline)-5-triazine in the presence of alkali and followed by reduction of nitro group was studied [4]. 

OB to C02 -54,3%, mp explds at approx 1S4°, hygr crysts. Prepd by dissolving m-nitroaniline in an excess of dil perchloric acid (d 1.12g/cc), the excess being such that, at the end of the reaction, free acid is present. A sufficient quantity nf Na nitrite in solid form or in a sstd soLp. is added to effect diazotization. The mixt is cooled during the Na nitrite addition ,... 

Metafor 3- Mononitrophenol Monoclinic prisms from eth or dil HC1 mp 97° bp 194° at 70mm, decomps when distd at ordinary pressure d 1.485g/cc at 20°, 1.2797 at 100°. Does not volatilize with steam cannot be prepd by the nitration of phenol. Can be obtained by boiling diazotized m-nitroaniline with w and sulfuric acid (Ref 3). SI sol in w, sol in ale. Highly toxic by ingestion and inhalation Refs 1) Beil 6, 222-24, (116), [212-14]... 

An increased hydrogen ion concentration, that is a considerably greater amount of acid than the theoretical two equivalents of Scheme 2-1, is necessary in the diazotization of weakly basic amines. The classic example of this is the preparation of 4-nitrobenzenediazonium ions 4-nitroaniline is dissolved in hot 5-10 m HC1 to convert it into the anilinium ion and the solution is either cooled quickly or poured onto ice. In this way the anilinium chloride is precipitated before hydrolysis to the base can occur. On immediate addition of nitrite, smooth diazotization can be obtained. The diazonium salt solution formed should be practically clear and should not become cloudy on standing in the dark. Some practice is necessary, and details can be found in the books emphasizing preparative aspects (Fierz-David and Blangey, 1952 Saunders and Allen, 1985 in Houben-Weyl, Vol. E 16a, Part II, the chapter written by Engel, 1990). These books give a series of detailed prescriptions for specific examples and a useful review of the principal variations of the methods of diazotization. Such reviews have also been written by Putter (1965) and Schank (1975). 

The so-called self-diazotization was developed by Sihlbohm (1951, 1953 a, 1953 b). It is based on the observation that several nitroaniline derivatives, on treatment with hydrochloric acid in acetic acid solution, form the corresponding chlorobenzenedi-azonium ions. 2,5-Dinitroaniline will serve as an example (Scheme 2-37). This reaction had already been discovered in principle by Meldola and Eyre in 1901. The method did not become important. 

The rate-determining step in the diazotization of aniline in aqueous perchloric acid below concentrations of 0.05 m (pH >0.7) is the formation of N203. The following A-nitrosation step is faster (rate equation of Scheme 3-12). However, with aromatic amines that are weaker nucleophiles than aniline, e.g. 4-nitroaniline, nitrosation is slower than the formation of N203, and the rate is second-order with respect to nitrous acid and first-order in amine (Scheme 3-13, Larkworthy, 1959). 

Fast blue salt B, fast blue salt BB, fast black salt K, diazotized sulfanilic acid (Pauly s reagent), diazotized sulfanilamide or 4-nitroaniline... 

Phenols (capable of coupling) Fast blue salt B, fast blue salt BB, fast black salt K, diazotized sulfanilic acid (Pauly s reagent) diazotized sulfanilamide or 4-nitroaniline Intensely colored azo dyes are formed. Catecholamines [20, 3S], imidazoles [21] and amines capable of coupling also react. [3, 17]... 

Sodium nitrite ers in this case the chromatograms are merely sprayed with sulfanilic acid solution (2% fTTlO mol hydrochloric acid) [5], Diazotized 4-nitroaniline can also be used in place of ... 

Azide 367 is prepared from 4-r -butyl-2-nitroaniline in 76% yield by its diazotization followed by treatment with sodium azide. In a 1,3-dipolar cycloaddition with cyanoacetamide, azide 367 is converted to triazole 368 that without separation is directly subjected to Dimroth rearrangement to give derivative 369 in 46% yield. Reduction of the nitro group provides ortfc-phenylenediamine 371 in 91% yield <2000EJM715>. Cyclocondensation of diamine 371 with phosgene furnishes benzimidazol-2-one 370 in 39% yield, whereas its reaction with sodium nitrite in 18% HC1 leads to benzotriazole derivative 372, which is isolated in 66% yield (Scheme 59). Products 370 and 372 exhibit potassium channel activating ability <2001FA841>. 

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