O Nitroaniline diazotization

In this case, the diazotization can be carried out satisfactorily according to the procedure given on page 246 for 3-nitro-4-toluidine, using 100 cc. concentrated hydrochloric acid and 120 g. ice for 0.25 mole o-nitroaniline. 

A mixture of 100 g. (0.75 mole) of o-nitroaniline and 500 ml. of a 1 1 mixture of water and concentrated hydrochloric acid is diazotized by the careful addition of an aqueous solution of 55 g. (0.80 mole) of sodium nitrite at 10°. The mixture is stirred for 15 minutes after the completion of the addition, the solution is filtered, and the filtrate is added slowly with agitation and cooling below 0° to 550 ml. of 25 sodium hydroxide solution. The resulting solution is added to a solution of 135 g. of sodium arsenite in 1250 ml. of water, and the mixture is heated to 60-70° for 2 hours, care being taken not to overheat it. This is followed by acidification with acetic acid, treatment with activated carbon, and the addition of hydrochloric acid until the mixture is strongly acid to Congo red. Cooling the mixture in ice precipitates 110 g. (61 ) of yellow powder, which after one recrystallization from water melts at 235-240° (dec.). 

Preparation. The precursor, l-chloro-4- o-nitrophenyl)-2-butene (3), is prepared by the Meerwein reaction of diazotized o-nitroaniline (2) with butadiene in acetone in the presence of cupric chloride and sodium acetate. - Dehydrohalogenation with methanolic potassium hydroxide then gives the diene (4). ... 

Aryl azides. In one synthesis of benzofurazane oxide (3) an aqueous solution of sodium azide is added to a solution of diazotized o-nitroaniline at 0-5°. Nitrogen is evolved, and o-nitrophenylazide separates as a light cream to colorless solid. Crystallization from 95% ethanol gives material (m.p. 52-54°) satisfactory for the... 

A number of other organic compounds is suitable for the diazotization and coupling reactions [62-69]. For example, the reaction with o-nitroaniline and N-(l-naphthyl)ethylenediamine leads to a method with e = 6.0-10 at 545 nm [68]. In some cases, 8-hydroxyquinoline is used for the coupling [70,71]. Many azo dyes formed by the use of various reagents are extractable [72-74]. In one of the methods [74], with hexanol as extractant, e = 5.2-10 at 610 nm. 

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. 

Dinitrobiphenyl has been prepared by the action of copper on o-chloronitrobenzene or 0-bromonitrobenzene,2 and on diazotized 0-nitroaniline.3... 

The new method of Yoneda s group132 is also a one-pot diazotization-fluoro-de-diazoniation in a liquid-liquid two-phase mixture of pyridine and hydrogen fluoride. Yields for 25 aromatic amines and diamines are 50-100%, except for 2-and 3-fluorobenzoic acid, the three nitroanilines, 3- and 4-diaminobenzene and 4,4 -diaminodiphenyl-oxide (10-50%). In their 1994 paper the authors demonstrate that, in the same system, the photochemical decomposition gives in many cases significantly higher yields than the thermal reaction. The most spectacular increase in yield was found for the fluorination of 2-fluoroaniline where o-difluorobenzene was obtained photochemically in 80.2% yield, but thermally only in 0.6% ... 

The 1,5-Bis (o ), mp 209 (m.-), mp 244°, and (p-), mp 262° derivs were prepd by Braun Rudolph (Ref 2) by nitrating the parent compd with a l/l mist of fuming nitric acid + sulfuric acid on a water bath. Horwitz Gra-kauskas (Ref 4) prepd the l,5-Bis(p-dinitro) deriv by coupling diazotized p-nitroaniline with 1-acetyl-2-(4,-bromo benzoyl) hydrazine, separating the tetrazole following cyclization l-(m-Nitrophenyl)-5-(p-nitrophenyl)-tetrazole, crysts, mp 170° (Ref 2)... 

Diazonium compounds other than phenyldiazonium chloride are also used, but to a smaller extent. Thus, in some plants, diazotized m-xylidine is used, but this appears to have no advantage since the diazonium solution is less stable. Diazotized p-aminoacetanilide, on the other hand, is used in certain cases because it couples more vigorously and gives a very stable solution (see chromotropic acid), o- and p-Nitroaniline are used less frequently. 

Diazotized p-Nitroaniline. Reacts with all phenols and amines. It must be kept in the dark, and after 1 to 2 days it gives a yellow color with soda alone, so care is necessary in its use. Diazotized o-chloroaniline can be used equally satisfactorily. 

The diaminobenzenes (phenylenediamines) are prepared by reduction of 1,3-dinitrobenzene and 2- and 4-nitroanilines. o-Phenylenediamine is of value in the synthesis of a range of nitrogen heterocycles. Thus reaction with organic acids produces benzimidazoles (8). With 1,2-dicarbonyl compounds, quinoxalines (9) are produced. Treatment with nitrous acid results in diazotization of one amino group followed by immediate cyclization to give benzotriazole (10). 

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