2-Naphthylamine, reaction with

Primary aromatic amines (e.g., aniline) and secondary aliphatic-aromatic amines (e. g., 7V-methylaniline) usually form triazenes in coupling reactions with benzenedi-azonium salts. If the nucleophilicity of the aryl residue is increased by addition of substituents or fused rings, as in 3-methylaniline and 1- and 2-naphthylamine, aminoazo formation takes place (C-coupling). However, the possibility has also been noted that in aminoazo formation the initial attack of the diazonium ion may still be at the amine N-atom, but the aN-complex might rearrange too rapidly to allow its identification (Beranek and Vecera, 1970). 

P-Bromonaphthalene. The preparation from p-naphthylamine, which has carcinogenic properties, is avoided by the use of 2-naphthylamine-1-sulphonic acid ( 2-amino-1-naphthalenesulphonic acid ) the latter is obtained commercially by cautious treatment of p-naphthol with sulphuric acid—the SOjH group first enters the 1-position—followed by the Bucherer reaction. Diazotisation and reaction with cuprous bromide yields 2-bromonaphthalene-l-sulphonic acid heating with sulphuric acid eliminates the sulphonic acid group to give 2-bromonaphthalene. 

The role of N-sulfonyloxy arylamines as ultimate carcinogens appears to be limited. For N-hydroxy-2-naphthylamine, conversion by rat hepatic sulfotransferase to a N-sulfonyloxy metabolite results primarily in decomposition to 2-amino-l-naphthol and 1-sulfonyloxy-2-naphthylamine which are also major urinary metabolites and reaction with added nucleophiles is very low, which suggests an overall detoxification process (9,17). However, for 4-aminoazobenzene and N-hydroxy-AAF, which are potent hepatocarcinogens in the newborn mouse, evidence has been presented that strongly implicates their N-sulfonyloxy arylamine esters as ultimate hepatocarcinogens in this species (10,104). This includes the inhibition of arylamine-DNA adduct formation and tumorigenesis by the sulfotransferase inhibitor pentachlorophenol, the reduced tumor incidence in brachymorphic mice that are deficient in PAPS biosynthesis (10,115), and the relatively low O-acetyltransferase activity of mouse liver for N-hydroxy-4-aminoazobenzene and N-OH-AF (7,114,115). 

Of the primary monoamines, some, such as. aniline, o-toluidine, xylidine, are colourless liquids. Others, such as p-toluidine, pseudo-cumidine and the naphthylamines, are solids. They can be distilled without decomposition and are volatile with steam. In water they are rather sparingly soluble—a 3 per cent solution of aniline can be made. The di- and polyamines are usually solids, not volatile in steam and much more soluble in water than the monoamines. The amines are basic in character, but, as a result of the negative nature of the phenyl-group, the aromatic amines are considerably weaker bases than are the aliphatic amines. Consequently aqueous solutions of the (stoicheio-metrically) neutral aniline salts are acid to litmus because of the hydrolysis which they undergo. For the same reason a small amount of the free base can be extracted with ether from an aqueous solution of an aniline salt. (Test with a solution of hydrogen chloride in ether or, after evaporation of the ether, by the reaction with bleaching powder.)... 

Figure 3. Relative fluorescence intensities of n-butylamine and aniline after reaction with o-phthalaldehyde, a-naphthylamine, and 7-hydroxycoumarin (O) aniline (O) n-butylaminej(A) a-naphthylamine (9) 7-hydroxycoumarin...

Reaction Lx x ill. Direct Replacement of the Aromatic Amino-group by Hydroxyl. (B., 7, 77, 809 D.R.P., 109102.)—The simple primary amino-groups in the benzene series are not easily replaced directly by hydroxyl unless an activating group (e.g., N02) be present in the o- or p-position. a-Naphthols, however, are readily obtained by heating a-naphthylamine derivatives with fairly concentrated acid under pressure. 

Unlike thioindoxyl (Section VI, 1,2), 4-hydroxybenzo[6]thiophene will not condense with aniline, nor will it undergo a Ullmann-Fetvadjian reaction with 1-naphthylamine.554... 

Like thioindoxyl (Section VI, 1,2) and 2-naphthol, but unlike thiooxindole (Section VI, 1,1) and 4-hydroxybenzo[6]thiophene (Section VI, 1,3), 5-hydroxybenzo[6]thiophene condenses readily with aromatic amines.558 It undergoes a normal Ullmann-Fetvadjian reaction with 1-naphthylamine to give l-methylthieno[3,2-u]benz[fe]-acridine, but with 2-naphthylamine an inseparable mixture of 1-methylthieno[3,2-u]benz[j]acridine and dibenz[u,j]acridine is obtained.558... 

In the reaction with a less basic amine such as aniline, mixtures of naphthylamines 153 and isoquinolinium salts 152 were obtained (71KGS1437 88UP2). The alternative pathway of formation of naphthylamines 153 from isoquinolinium salts 152 by isomeric recyclization (81T3425) is completely excluded, since model experiments with isoquinolinium salts showed no reaction under the conditions of synthesis of naphthylamines 153. 

The application of acetic acid catalysis in reaction of 2-benzopyrylium salts with primary amines4, in contrast to the reaction with ammonia, does not lead to a simple result. Thus, if in 30 R3 is not Aik, excluding the alternative formation of a-naphthylamines of type 153, the use of acetic acid catalysis leads to isoquinolinium salts 152 in high yields (89KPS75), whereas without acetic acid, diketones 166 were the only products of interaction between 2-benzopyrylium salts 30 and primary amines. 

For benzo[c]pyrylium salts having different alkyl substituents in positions a(l) and a (3), the reaction with secondary amines loses its predictable regioselectivity. Thus, reaction with dimethylamine, independent of the solvent, gives rise to /3-naphthylamine 185, from l-ethyl-3-methyl-substituted salt 183 (81KGS1608), and a-naphthylamine 186 from 1-benzyl derivative 184 (88UP1). In the former case, the nucleophilic attack occurs in position 3, whereas in the latter case, it takes place in position 1. 

The direct replacement of the hydroxyl group in simple phenols by an amino or substituted amino group requires drastic conditions and the method is not suitable for laboratory preparations. With the polyhydric phenols, and more particularly with the naphthols, such replacements occur more readily. Thus 2-naphthol is converted into 2-naphthylamine by heating with ammoniacal ammonium sulphite solution at 150°C in an autoclave. The reaction (the Bucherer reaction) depends upon the addition of the hydrogen sulphite ion to the keto form of the naphthol and the subsequent reaction with ammonia. 

Messmer and Sziman measured the coupling rates of p-methoxybenzene-diazonium tetrafluoroborate with N,N-dimethylaniline, m-toluidine and 1- and 2-naphthylamine in nitrobenzene as solvent. Except for reactions with m-toluidine, the reaction rates were reduced significantly if a deuterium ion had to be displaced instead of a proton. The kinetic isotope effect varied from k /kp = 1.5 for 2,4,6-dj-... 

Therefore Rufer studied an azo coupling reaction with uncharged coupling components, namely that of p-methoxybenzenediazonium ions with 1-naphthylamine and l-amino-2-methylnaphthalene, buffered to pH 7 at 25 °C. Both reactions are strongly catalyzed by sodium dodecylsulfate (up to 1100 times with l-amino-2-methyl-naphthalene) in cases where the surfactant concentration was higher than the critical micelle concentration (CMC). For the coupling reaction with 1-naphthylamine, both the o/p-ratio and the amount of the 2,4-bisphenylazo product are dependent on the sodium dodecylsulfate concentration. The formation of the 2,4-bisphenylazo com-... 

In a preliminary communication Sziman and Messmer reported kinetic deuterium isotope effects in C-coupling reactions of 4-methoxybenzenediazonium tetra-fluoroborate with N,N-dimethylaniline, m-toluidine, 1- and 2-naphthylamine in nitrobenzene solution (k /kjj = 1.5, 1.0, 3.3 and-4.4, respectively). As it has b n mentioned that all such reactions are base catalyzed, it is difficult to understand why the reaction with m-toluidine does not display an isotope effect. As shown in Section 4.4, azo coupling reactions with aromatic amine may be rather complex with respect to mechanism. A critical discussion of Sziman and Messmer s paper is therefore impossible. Although announced in their conununication, a full paper has to the best of our knowledge, never been published. 

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