Bromination aromatic amines

MDA reacts similarly to other aromatic amines under the proper conditions. For example, nitration, bromination, acetylation, and dia2oti2ation (1 3) all give the expected products. Much of the chemistry carried out on MDA takes advantage of the diftmctionality of the molecule in reacting with multiftmctional substrates to produce low and high molecular weight polymers. 

A Methylanthrapyridone and Its Derivatives. 6-Bromo-3-methylanthrapyridone [81-85-6] (75) is an important iatermediate for manufacturiag dyes soluble ia organic solvents. These solvent dyes are prepared by replacing the bromine atom with various kiads of aromatic amines. 6-Bromo-3-methylanthrapyridone is prepared from 1-methyl amino-4-bromoanthra quin one (43) by acetylation with acetic anhydride followed by ring closure ia alkaU. The startiag material of this route is anthraquiaoae-l-sulfonic acid (16). 

Further organic storing materials Phenyl bromide [14], pyridine, 1 -picoline, 2,6-lutidine [15-17] Arsonium salts [18, 19] Phosphonium salts [20] Pyridinium bromides [21] Aromatic amines [22] Urotropin-bromine adduct [23] Pyridinium and sulfonium salts [24] Propionitril [25]... 

Acrylonitrile, CH2= HCN Bromine addn or a trace of alkali Acrylonitrile Vapor 6000 kg/cm2 >200 Ammonia or Aromatic Amine as an inhibitor 17.3 481 Sensitive to light, strong bases or temps > 200°... 

The dienone, which is prepared essentially as described by Benedikt7 and Calo,8 monobrominates a wide range of primary, secondary, and tertiary aromatic amines almost exclusively in the para-position. The procedure described is of general synthetic utility for the preparation of para-brominated aromatic and heteroaromatic amines in high yields and frequently in a high state of purity. The submitters have used this technique to para-brominate many compounds in quantities... 

Our recent studies on effective bromination and oxidation using benzyltrimethylammonium tribromide (BTMA Br3), stable solid, are described. Those involve electrophilic bromination of aromatic compounds such as phenols, aromatic amines, aromatic ethers, acetanilides, arenes, and thiophene, a-bromination of arenes and acetophenones, and also bromo-addition to alkenes by the use of BTMA Br3. Furthermore, oxidation of alcohols, ethers, 1,4-benzenediols, hindered phenols, primary amines, hydrazo compounds, sulfides, and thiols, haloform reaction of methylketones, N-bromination of amides, Hofmann degradation of amides, and preparation of acylureas and carbamates by the use of BTMA Br3 are also presented. 

Berthelot et al. have already reported that the reaction of aromatic amines with tetrabutylammonium tribromide (TBA Br3) in chloroform gave p-selective bromo-substituted aromatic amines (ref. 10). We also carried out the bromination of... 

Combined effect of BTMA Br3 and ZnCl2 in acetic acid provides a new excellent bromination procedure for arenes. That is, while such reactive aromatic compounds as phenols, aromatic amines, aromatic ethers, and acetanilides have been easily brominated by BTMA Br3 in dichloromethane in the presence of methanol, the reaction of arenes, less reactive compounds, with BTMA Br3 in dichloromethane-methanol did not proceed at all, even under reflux for many hours. However, arenes could be smoothly brominated by use of this agent in acetic acid with the aid of the Lewis acid ZnCl2 (Fig. 13) (ref. 16). 

Nucleophilic substitution reactions, to which the aromatic rings are activated by the presence of the carbonyl groups, are commonly used in the elaboration of the anthraquinone nucleus, particularly for the introduction of hydroxy and amino groups. Commonly these substitution reactions are catalysed by either boric acid or by transition metal ions. As an example, amino and hydroxy groups may be introduced into the anthraquinone system by nucleophilic displacement of sulfonic acid groups. Another example of an industrially useful nucleophilic substitution is the reaction of l-amino-4-bromoanthraquinone-2-sulfonic acid (bromamine acid) (76) with aromatic amines, as shown in Scheme 4.5, to give a series of useful water-soluble blue dyes. The displacement of bromine in these reactions is catalysed markedly by the presence of copper(n) ions. 

Among the most important indirect methods of analysis which employ redox reactions are the bromination procedures for the determination of aromatic amines, phenols, and other compounds which undergo stoichiometric bromine substitution or addition. Bromine may be liberated quantitatively by the acidification of a bromate-bromide solution mixed with the sample. The excess, unreacted bromine can then be determined by reaction with iodide ions to liberate iodine, followed by titration of the iodine with sodium thiosulphate. An interesting extension of the bromination method employs 8-hydroxyquinoline (oxine) to effect a separation of a metal by solvent extraction or precipitation. The metal-oxine complex can then be determined by bromine substitution. 

SCHEME 185. Chlorination and bromination of aromatic amines, hydrocarbons and naphthols with in situ generated active halogen... 

Amberlite XAD-2 and XAD-4 resins, for example, contain significant quantities of alkyl derivatives of benzene, styrene, naphthalene, and biphenyl as received from the supplier. PUF products, on the other hand, generally contain numerous contaminants peculiar to one of the several patented commercial manufacturing processes. These include, but are not limited to, the following classes of chemical contaminants isocyanate derivatives (e.g., toluene diisocyanates), alkyl amines, aliphatic acids, and brominated aromatics (e.g., fire retardants). 

Reaction CXXXVII. Action of Bromine (or Chlorine) and Alkali on certain Amides and Imides (Hoffmann s Reaction).—-This method is applicable for the preparation of both aliphatic and aromatic amines. 

For chlorination, the formation of the (7-complex would be expected to be the rate-determining step since the aromatic chlorination of other substrates does not appear to give rise to deuterium isotope effects (Baciocchi et al., 1960 de la Mare and Lomas, 1967). The effect of the experimental conditions on the rate-determining step in the aqueous bromination of aromatic amines has been investigated in detail by Dubois and his co-workers (Dubois et al., 1968a, b, c Dubois and Uzan, 1968). This work suggests that, for tertiary aromatic amines, the proton loss is fast for para-bromination but partly or wholly rate-determining for ortho-bromination. There is however some... 

Most of the rate comparisons in the halogenation of aromatic amines refer to bromination rate coefficients for para-substitution are collected in Table 10. Further results for o/7/io-substitution are provided in the cited references. Some of the early calculation based on (39) and (40) may be in error, because it was not then realized that the appropriate acidity function in (40) depends on the structure of the substrate (cf. Bell and Ramsden., 1958 Bell and Ninkov, 1966). The appropriate acidity function was used for the results listed in Table 10 but it is still advisable for rate comparisons to be based on experiments carried out under the same conditions. 

Rate coefficients (k, eqn 39) for the para-bromination of aromatic amines... 

In most of the recorded deaminations with ethanol, sulfuric acid has been used rather than hydrochloric or nitric acid. As a general practice this appears to be a good choice since, in certain cases, diazotization with hydrochloric acid involves a risk that the deamination product may contain chlorine in place of a bromine atom or a nitro group originally present in the aromatic amine. ... 

We haven t yet discussed amine protection (that will come later in this chapter) but, since it is the amino group s nucleophilicity that is the problem, it makes sense to react it with an acylating agent an amide is much less nucleophilic than an amine because the nitrogen s lone pair is involved in conjugation with the carbonyl group. The same method was used to reduce the nucleophilicity of aromatic amines in bromination (Chapter 22). The carboxylic acid also needs protecting, and it is made into an ethyl ester. 

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