Diazotized aniline

The most important reaction of the diazonium salts is the condensation with phenols or aromatic amines to form the intensely coloured azo compounds. The phenol or amine is called the secondary component, and the process of coupling with a diazonium salt is the basis of manufacture of all the azo dyestuffs. The entering azo group goes into the p-position of the benzene ring if this is free, otherwise it takes up the o-position, e.g. diazotized aniline coupled with phenol gives benzeneazophenol. When only half a molecular proportion of nitrous acid is used in the diazotization of an aromatic amine a diazo-amino compound is formed. 

Yields can be very good Beyer (402) reports a 90% yield when coupling 2-amino-4-phenylthiazole with the diazonium salt of aniline. The coupling of diazotized anilines under modified conditions has been reported in a work treating the preparation of antineoplastics (403). 

The method described here is a modification of that of Schoeller.1 Diphenyl selenide has also been prepared from diazotized aniline and alkali monoselenides 2 by the Friedel-Crafts reaction with benzene and selenium tetrachloride3 or selenium dioxide 4 from diphenyl sulfone and selenium 5 from phenylmagnesium bromide and selenium,6 selenium dichloride,7... 

Our task was to develop a feasible synthesis for diamino resorcinol. From several possibilities [1-4] the resorcinol and anihne were chosen as starting materials. The diazotated aniline was coupled with resorcinol among basic conditions giving 4,6-bisphenylazo resorcinol. Hydrogenation of the latter resulted in diamino resorcinol and aniline, which could be recycled (scheme 14.2). This chemistry is well known [5-13] therefore, the research work focused on finding the optimal parameters and catalyst and finally on elaborating a process for scale-up. 

Kirk Othmer II (1966), 864 l-Azido-2-iodobenzene, C6H4N3I mw 245.03, N 17.15% strong smelling oil, bp 90-91° at 0.9 mm Hg, d 1.8893 at 25°, refractive index 1.6631 at 25° prepd by diazotizing aniline with NaN3. No expl props are reported. The l-Azido-3-iodo- and 1-Azido-4-iodo-derivs are also known (Ref 2)... 

Salicylic acid couples with diazonium salts in the expected manner. With diazotized aniline, ie, benzenediazonium chloride, the primary product is 5-phenylazosalicylic acid [3147-53-3] (eq. 7). 

Similar coupling of diazotized anilines with 2-chloro-1-(2-fury 1)-1,3-butanedione 107D under similar conditions gave the 2-(2-furyl)-2-oxo-N-arylethanehydrazonoyl chlorides 29 (82H57). 

When treated with aniline, diazotized aniline (benzenediazonium chloride) yields, apart from a small quantity of 4-aminoazobenzene (33), diazoaminoben-zene (34) as the main product ... 

Whereas p -naphthylaminesulfonic acids always couple at the adjacent a position, in a-naphthylaminesulfonic acids, the coupling location is influenced by the position of the sulfonic acid group 1,6-, 1,7-, and 1,8-naphthylaminesulfonic acids couple at the 4-position 1,5-naphthylaminesulfonic acid (Laurent acid) only couples with very strong couplers (e g., 2,4-dinitroaniline), mainly at the 4-position. With diazotized aniline, chloroaniline, or diazotized aniline sulfonic acids the 2-aminoazo dyes are obtained, but with diazotized nitroaniline, mixtures of the 2-and 4-coupling products form (Scheme 2.1). 

The dye 10 is obtained by simultaneous coupling of one equivalent each of diazotized aniline and 4-aminoacetanilide to I-acid urea (6). 

Coupling diazotized dehydrothio-p-toluidinesulfonic acid to resorcinol and subsequent coupling of diazotized aniline to the monoazo dye formed gives C. I. Direct Orange 18, 20215 [5915-59-3] (11), an important substantive dye. 

Amides of 3- or 6-hydroxy-2-naphthoic acid bearing dialkylaminoalkyl residues on the nitrogen atom lead to orange dyes for polyacrylonitrile or paper when coupled with diazotized aniline [20,21] or to red dyes, soluble in glycol ethers and useful for ink-jet printing, when coupled with diazotized 3-amino-4-methoxybenzenesulfonic acid AOV-dicthylam idc [22], and to substantive red dyes when the diazo component is a 2-(4 -aminophenyljbenzotriazole [23],... 

A limitation of both methods is that the second component must be liquid at the temperature of-the reaction, which is 5-10° for the diazohydroxide reaction and room temperature or slightly higher for the nitrosoacetylamine reaction. Experiments with solid reactants in solution have not been very successful, because of the difficulty of finding a suitable solvent. The solvent should be neutral and immiscible with water, have a high solvent action and reasonably low boiling point, and be inert to the free radicals which result from the diazo compound. The last qualification is the most difficult one to satisfy. Of the solvents which have been tried, carbon tetrachloride and chloroform appear to be the most suitable.18 From diazotized aniline and biphenyl in these solvents, some p-terphenyl is obtained, and from diazotized p-nitroaniline and biphenyl a small amount of 4-nitro-4 -phenylbiphenyl is formed. In these reactions an appreciable amount of tfie aryl halide (chlorobenzene and p-nitrochlorobenzene) is produced as a by-product. In general, the yields of products obtained by coupling with reactants in solution are extremely low. 

For the preparation of biphenyl compounds with substituents in only one ring, it is usually advisable to employ a substituted aniline and couple with benzene rather than to use aniline and couple with a benzene derivative, since with benzene only a single biaryl compound is produced. Thus, 4-methylbiphenyl can be isolated readily in pure form from the reaction between diazotized p-toluidine and benzene, but not from the mixture of 2- and 4-methylbiphenyl formed from diazotized aniline and toluene. 

However, isolation of the product or products formed by coupling with nitrobenzene and certain other compounds has been successful. From nitrobenzene and diazotized aniline (in the form of the stabilized diazo-nium salt), 4-nitrobiphenyl is obtained in 33% yield, and from o-nitro-... 

It is not possible to prepare biaryls containing a free carboxyl group directly by the diazo reaction. No biaryl is formed when (a) diazotized aniline and sodium benzoate, (b) diazotized anthranilic acid and aqueous sodium benzoate, or (c) diazotized anthranilic acid and benzene are used as components in the reaction.13 On the other hand, the reaction proceeds normally if methyl benzoate is used in reaction (a) or when methyl anthranilate replaces the anthranilic acid in (b) and in (c). The success of the diazohydroxide reaction appears to lie in the ability of the non-aqueous liquid to extract the reactive diazo compound from the aqueous layer.4 However, esters and nitriles can be prepared from esters of aromatic amino acids and cyanoanilines and also by coupling with esters of aromatic acids, and from the products the acids can be obtained by hydrolysis. By coupling N-nitrosoacetanilide with ethyl phthalate, ethyl 4-phenylphthalate (VIII) is formed in 37% yield. 

One of the side reactions is the formation of linear polyaryls, which may be considered to be formed by further reaction of the biaryl initially produced. From the high-boiling residue remaining after the removal of the biphenyl, formed from diazotized aniline, benzene, and alkali, p-terphenyl and quaterphenyl16 have been isolated and in the mixture formed in the preparation of 4-methylbiphenyl a hydrocarbon was found... 

Hydroxy derivatives of biphenyl can be prepared from diazonium salts, such as the chloride or sulfate, and phenols if no alkali is added.28- 29, 30 31-32 From a solution of diazotized aniline in a large excess of-phenol, a good yield of a mixture of 2- and 4-hydroxybiphenyl is obtained in addition to diphenyl ether. 

From diazotized aniline and p-nitrosophenol Borsche 88 obtained 2-hy-droxy-5-nitrosobiphenyl (XXIII) in 8% yield, and with 2-methyl-4-ni-trosophenol he obtained 2-hydroxy-3-methyl-5-nitrosobiphenyl (XXIV). 

Gomberg and Pemert4 recommended the use of the sodium diazotates for the preparation of biaryls from aniline and from p-toluidine and the normal diazo method for negatively substituted amines such as the bromo- and nitro-anilines. Grieve and Hey 7 found little difference in the yields of biaryls obtained by the two procedures when they coupled diazotized aniline with six different components benzene, toluene, m-xylene, chlorobenzene, nitrobenzene, and ethyl benzoate. Where it is applicable, this modification offers the advantage that the dropwise addition of alkali is eliminated. 

The effect of various other reagents on the yield of biphenyl from diazotized aniline and benzene has been studied. The following yields of biphenyl were obtained from one mole of aniline under the conditions noted.18 46... 

The above mentioned authors have diazotized aniline with the complex and obtained fluorobenzene. 

Allied with the chromatography of imidazoles have been methods of estimation of the compounds, particularly those of biological importance, either on the chromatograms or after elution. Most workers have used diazotized aromatic amines as colorimetric reagents,53,277-285 particularly nonsulfonated diazotized aniline derivatives.281-285 Mosebach et aZ.286 initially hydrolyzed. -substituted imidazoles with 10 A hydrochloric acid before separating the compounds by ion-exchange and paper chromatographic techniques prior to estimation. A number of other methods exist for the colori-... 

Since salicylic acid is not easily nitrated or nitrosated, p-aminosalicylic acid is usually prepared by reduction of the azo dye from diazotized aniline and salicylic acid, accor ng to the following equations ... 

To the diazo solution is added a solution made from 31 grams of aniline, 200 cc. water, 100 grams of ice, 40 cc. 2 N acetic acid, and 120 cc. 2 N hydrochloric acid, and the mixture is allowed to stand for 10 minutes. A solution of 50 cc. 25 per cent ammonia in 400 cc. water is then added, with continuous stirring, at such a rate that the reaction mixture stays distinctly acid to litmus at all times. The ammonia should be added below the surface of the reaction mixture. The addition requires 2 to 3 hours, after which the reaction mixture gives no test for diazotized aniline with H acid solution. The yellow diazoamino com-... 

The amine is titrated with hydrochloric acid and sodium nitrite in very dilute solution, and the resulting diazonium salt is coupled with an accurately known amount of a phenol, usually SchaefiFer salt. With other compounds, such as H acid, amino R acid, etc., one sample is diazotized and another is coupled with diazotized aniline or other amine. Under some circumstances it is possible to determine two substances in mixture if one of them reacts much more rapidly than the other. Thus, with a little practice, one can determine quite accurately both G salt and R salt in mixtures of.the two. R salt couples very rapidly with diazotized aniline producing a red dye, while G salt couples more slowly and gives a yellow dye. A large number of other special methods are available which permit the determination of the individual constituents in mixtures. 

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