Reactions of Aromatic Amines

The amino group is strongly electron donating and directs substitution to the ortho and para positions. This is illustrated by the addition of chlorine or bromine water to aniline, which results in immediate reaction and the precipitation of the 2,4,6-trihalogenated derivative. 

The amino group is a reactive species and undergoes some important reactions. 

The 4-isomer is the major product because attack at the 2-position is sterically hindered. Nevertheless, ca. 10% of 2-bromoacetaniiide is produced during the bromination of acetanilide. 

A quaternary atom has four organic substituents attached to it. Quaternization is the process of attaching the fourth substituent. 

A/-Methylaniline may be formylated with formic acid (methanoic acid, HCO2H). The product, A/-methylformanilide (6), is used as a formylating reagent. 

ilCtlt M WiMt ff iC nrfii.n / liiiTirtinq froc l -nnv n..ii i nnl. n. -vitl-r- dift.n tiircj iHni.tinn of 

If II I Hure nl undanf -jniliniLim n a i nixlursfi result. Rfcanlioi iS riCti nijitnjnatin  

Nevoritietosv a O- ut 7 Iti Piuao.-taiiilulo is produced luring Ml. pi . iinnati ii ( riceto uii-jfi 

Amines can be reductively alkylated by aldehydes and ketones in the presence of hydrogen and a hydrogenation catalyst. 

Q Explain how an A-isopropyl group might be introduced into aniline by a reductive alkylation technique. 

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SchifT s bases A -Arylimides, Ar-N = CR2, prepared by reaction of aromatic amines with aliphatic or aromatic aldehydes and ketones. They are crystalline, weakly basic compounds which give hydrochlorides in non-aqueous solvents. With dilute aqueous acids the parent amine and carbonyl compounds are regenerated. Reduction with sodium and alcohol gives... 

Aluminum chloride [7446-70-0] is a useful catalyst in the reaction of aromatic amines with ethyleneknine (76). SoHd catalysts promote the reaction of ethyleneknine with ammonia in the gas phase to give ethylenediamine (77). Not only ammonia and amines, but also hydrazine [302-01-2] (78), hydrazoic acid [7782-79-8] (79—82), alkyl azidoformates (83), and acid amides, eg, sulfonamides (84) or 2,4-dioxopyrimidines (85), have been used as ring-opening reagents for ethyleneknine with nitrogen being the nucleophilic center (1). The 2-oxopiperazine skeleton has been synthesized from a-amino acid esters and ethyleneknine (86—89). 

Condensation. Depending on the reaction conditions, a variety of condensation products are obtained from the reaction of aromatic amines with aldehydes, ketones, acetals, and orthoformates. 

Radical Trapping. Figure 2 shows some of the reactions of aromatic amines that contribute to their activity as antioxidants and to their tendency to form highly colored polyconjugated systems. 

Reaction of a-isocyano-a, / -unsaturated sulfones with primary aliphatic amines affords 1,5-disubstituted imidazoles 59 (equation 56)48. The reaction of aromatic amines such as aniline is too slow to be of practical use. Results of the preparation of 59 are listed in Table 5. 

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... 

Peroxides oxidize TPDD to Wurster s blue, a product with a semiquinone diimine structure [1]. Similarly Wurster s blue is also produced from TPDD by reaction with halogen-containing substances produced by the reaction of aromatic amines and triazines with chlorine gas. 

Reaction of Aromatic Amines with Peroxyl Radicals... 

REACTION OF AROMATIC AMINES WITH PEROXYL RADICALS... 

The former are formed by the reaction of aromatic amines and NO in the atmosphere whereas the latter are formed during combustion processes. N-nitroso compounds have been studied extensively and some of them are discussed below. 

As previously discussed, activation of the iridium-phosphoramidite catalyst before addition of the reagents allows less basic nitrogen nucleophiles to be used in iridium-catalyzed allylic substitution reactions [70, 88]. Arylamines, which do not react with allylic carbonates in the presence of the combination of LI and [Ir(COD)Cl]2 as catalyst, form allylic amination products in excellent yields and selectivities when catalyzed by complex la generated in sim (Scheme 15). The scope of the reactions of aromatic amines is broad. Electron-rich and electron-neutral aromatic amines react with allylic carbonates to form allylic amines in high yields and excellent regio- and enantioselectivities as do hindered orlAo-substituted aromatic amines. Electron-poor aromatic amines require higher catalyst loadings, and the products from reactions of these substrates are formed with lower yields and selectivities. 

Weber, E.J., Colon, D., and Baughman, G.L. Sediment-associated reactions of aromatic amines. 1. Elucidation of sorption mechanisms. Environ. Sci. Technol, 35(12) 2470-2475, 2001. 

The main problem encountered during electrophilic substitution reactions of aromatic amines is that of their veiy high reactivity. Substitution tends to occur at ortho- and para-positions. If we have to prepare monosubstituted aniline derivative, how can the activating effect of -NH group be controlled This can be done by protecting the -NH group by acetylation with acetic anhydride, then carrying out the desired substitution followed by hydrolysis of the substituted amide to the substituted amine. 

The reaction of aromatic amines with tetrazine (151) gave either 1,2,4-triazoles (154) or pyrazolo[4,3-e]-l,2,4-triazines (155), depending on the substituents. While aniline, p-toluidine, p-anisidine and p-chloroaniline afford 155, the bromo and p-nitro derivatives give 154. Intermediates 152 and 153 were postulated (Scheme 22) (82CB683). 

The two key isocyanates that are used in the greatest volumes for polyurethane polymers are toluene diisocyanate (TDl) and methylene diphenyl diisocyanate (MDl). Both isocyanates are produced first by nitration of aromatics (toluene and benzene, respectively), followed by hydrogenation of the nitro aromatics to provide aromatic amines. In the case of MDl, the aniline intermediate is then condensed with formaldehyde to produce methylene dianiline (MDA), which is a mixture of monomeric MDA and an oligomeric form that is typical of aniline/formaldehyde condensation products [2]. The subsequent reaction of phosgene with the aromatic amines provides the isocyanate products. Isocyanates can also be prepared by the reaction of aromatic amines with dimethylcarbonate [3, 4]. This technology has been tested at the industrial pilot scale, but is not believed to be practiced commercially at this time. 

Zhang J, Li C-J (2002) InCl3-catalyzed domino reaction of aromatic amines with cyclic enol ethers in water a highly efficient synthesis of new L2,3,4-tetrahydroquinoline derivatives. J Org Chem 67 3969-3971... 

The enamine adducts formed in the reaction of aromatic amines with DMAD have been found to undergo cyclization leading to heterocyclic compounds, and the mode of these reactions is to a considerable extent influenced by the reaction conditions, the catalyst employed, and also the nature of the functional groups present in the starting amine. The reaction of aniline with methyl propiolate in presence of cuprous acetate, for example, is reported to give a mixture of 2(lH)-quinolone (1) and 4(l//)-quinolone (2) [Eq. (1)]." On the other hand, dimethyl anilinofumarate (3), formed from aniline with DMAD, undergoes... 

The high-temperature reaction of aromatic amines with aromatic nitro compounds in the presence of base affords primarily an azo compound [39,40]. Because two independent laboratories have reported reasonable results with this synthesis, the procedure is given here. To be noted is that, while the reaction as described here involves 2-naphthylamine, a known carcinogenic intermediate, it is given only for reference to the procedure. Evidently, other aromatic amines also undergo the reaction. 

The phenolic group is activating and ortho-para directing. The electrophilic substitution reactions in the nucleus in (a) nitrosation and nitration (b) halogenation and (c) acylation and alkylation, are therefore particularly facile, and various experimental procedures need to be adopted to control the extent of substitution (cf. substitution reactions of aromatic amines and their acylated derivatives, Sections 6.6.1 and 6.6.2, pp. 906 and 916 respectively). 

Yinylogous enamine dyes are obtained by reaction of aromatic amines with mucochloric acid (2,3-dichloro-4-oxo-2-butanoic acid), followed by condensation with quaternary quinaldine. After methylation of the enamine nitrogen atom with dimethyl sulfate, the dye 5 is obtained, which dyes bleached sulfite pulp red [15]. 

Another class of substances of interest as bifunctional diazo components consists of special diamines that can be manufactured by the reaction of aromatic amines with benzaldehyde or cyclohexanone, e.g.,16 and 16a. 

Surface water i/2 = 0.62.4-3840 h, based on estimated rate constants for reactions of aromatic amines with OH and R02 radicals in aqueous solutions (Howard et al. 1991). 

Surface water t,/2 = 62.0-3840 h, based on estimated rate constants for reactions of aromatic amines with OH and R02 radicals in aqueous solutions (Giiesten et al. 1981 Mill Mabey 1985 quoted, Howard et al. 1991). Groundwater t1/2 = 1344-8640 h, based on estimated unacclimated aqueous aerobic biodegradation half-life (Howard et al. 1991). 

An InCl3-catalyzed domino reaction of aromatic amines and cyclic enol ethers has been reported and gives rise in good yields to a range of 2,3,4-trisubstituted 1,2,3,4-tetrahydroquinolines <2002JOC3969>. 

E. Ochiai, Aromatic Amine Oxides. Am. Elsevier, New York, 1967. V-Oxides, photochemical reactions of aromatic amine ... 

The reaction of aromatic amines with nitrous acid is of considerable importance and the formation of diazonium salts from the primary amines is discussed in detail in Section 8.6. Reaction of nitrous acid with secondary amines does not give diazonium salts, but results instead in A -nitrosation. Tertiary amines such as A, A -dimethylaniline do not N-nitrosate, but undergo electrophilic substitution by the nitrosonium cation (NO ) to give A, A -dimethyl-4-nitrosoaniline (Scheme 8.8). 

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