Aromatic amines deamination

Other Applications. Hydroxylamine-O-sulfonic acid [2950-43-8] h.2is many applications in the area of organic synthesis. The use of this material for organic transformations has been thoroughly reviewed (125,126). The preparation of the acid involves the reaction of hydroxjlamine [5470-11-1] with oleum in the presence of ammonium sulfate [7783-20-2] (127). The acid has found appHcation in the preparation of hydra2ines from amines, aUphatic amines from activated methylene compounds, aromatic amines from activated aromatic compounds, amides from esters, and oximes. It is also an important reagent in reductive deamination and specialty nitrile production. 

Aminoisothiazoles have all been prepared by nitration and subsequent reduction, usually in good yield, although the reduction of 4-nitroisothiazole to 4-aminoisothiazole has only been achieved in 35% yield. 4-Aminoisothiazoles behave as normal aromatic amines and the diazonium salts undergo the Sandmeyer reaction and reductive deamination. ... 

Dichloronitrobenzene has been prepared by deamination of 3,5-dichloro-4-nitroaniline and of 2,4-dichloro-3-nitroaniline. This procedure is an example of the rather general oxidation of anilines to nitrobenzenes with peroxytrifluoroacetic acid. Use of this reagent is frequently the method of choice for carrying out this transformation, and it is particularly suitable for oxidation of negatively substituted aromatic amines. Conversely, those aromatic amines, such as />-anisidine and j8-naphthylamine, whose aromatic nuclei are unusually sensitive to electrophilic attack give intractable mixtures with this reagent. This is not... 

Monoamine oxidase catalyzes the deamination of primary amines and some secondary amines, with some notable exceptions. Aromatic amines with unsubstituted a-carbon atoms are preferred, but aromatic substituents influence the binding of these substrates. For example, m-iodobenzylamine is a good substrate, whereas the o-iodo analog is an inhibitor. The mechanism of deamination is as follows hydrolysis of the Schiff base that results from loss of a hydride ion on an a-proton yields an aldehyde, which is then normally oxidized to the carboxylic acid. Aromatic substrates are probably preferred because they can form a charge-transfer complex with the FAD at the active site, properly... 

The enzyme found in the liver will deaminate secondary and tertiary aliphatic amines as well as primary amines, although the latter are the preferred substrates and are deaminated faster. Secondary and tertiary amines are preferentially dealky la ted to primary amines. For aromatic amines, such as benzylamine, electron-withdrawing substituents on the ring will increase the reaction rate. The product of the reaction is an aldehyde (Fig. 4.30). Amines such as amphetamine are not substrates, seemingly due to the presence of a methyl group on the a-carbon atom (Fig. 4.27). Monoamine oxidase is important in the metabolic activation and subsequent toxicity of allylamine (Fig. 4.31), which is highly toxic to the heart. The presence of the amine oxidase in heart tissue allows metabolism to the toxic metabolite, allyl aldehyde (Fig. 4.31). Another example is the metabolism of MPTP to a toxic metabolite by monoamine oxidase in the central nervous system, which is discussed in more detail in chapter 7. 

This method of deaminating aromatic amines appears to be of general applicability, particularly to benzidine and its derivatives. Benzidine itself has been deaminated in 60 per cent yield. The use of hypophosphorous acid in preference to alcohol for these deaminations arises from the fact that this procedure is much simpler, the yields are higher, and the products are of better quality. 

This use of hypophosphorous acid for the deamination of aromatic amines appears to have originated with Mai.1 Recently it has been used for this purpose by Raiford and Oberst.2... 

Biodegradation. Nitrosubstituted compounds are subject to a variety of degradative processes. Under anaerobic conditions TNT is readily reduced to the corresponding aromatic amines and subsequently deaminated to toluene. As shown in the section on hydrocarbons, Llie latter can be mineralized under anaerobic conditions, leading to the potentially complete mineralization of TNT in the absence of oxygen. 

It is evident that the success of the deamination process is a function of the completeness of diazotization as well as of the reduction. Fortunately, practically any primary aromatic amine is susceptible of diazotization, usually in yields approaching the theoretical. The conditions for this reaction are comparatively standard and are fully described in monographs on the diazo compounds.1... 

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. ... 

This is not the only instance where hypophosphorous acid is more effective than ethyl alcohol. For example, whereas deamination of o-toluidine by the hypophosphorous acid procedure affords toluene in 70-75% yield,82 treatment with ethanol gives o-ethoxytoluene in approximately 50% yield.10-13 And while reduction of the diazonium salt of p-amino-phenylarsonic acid by hypophosphorous acid yields phenylarsonic add (ca. 50%),92 ethanol gives p-ethoxyphenylarsonic add (ca. 65%). Although 3,3 -dimethoxybenzidine may be deaminated by either procedure, the yield with hypophosphorous acid is 66-78% 80 81 as compared to approximately 20% when ethanol is used.46 These data, in conjunction with other results, lead to the conclusion that hypophosphorous acid is at least equal to ethanol as a reagent for deaminating an aromatic amine, and that it is usually effective in deaminations which cannot be carried out with ethanol.18 81 82-88187 93 94... 

Aromatic amines and their homologs are converted to the corresponding hydrocarbons in 60-80% yields with alkoxy- and aryloxy-amines, the yields range from 50 to 75%.4 The deaminations of 2,4-dimethyl-... 

Certain primary aromatic amines that are available as a consequence of their use in the manufacture of dyes serve as convenient starting points in the preparation of organic compounds. Their range of utility is increased by the deamination reaction. The syntheses of 2,2 -dinitro-5,5 -dicarboxybiphenyl from o-tolidine38 and of 3,3 -dihydroxybiphenyl from o-dianisidine 80 are examples. 

The method of synthesis described herein is the best procedure for preparing unsymmetrically substituted sulfamides, but it can be applied also to the symmetrically substituted ones. However, it may be a longer procedure for the latter, although the yields obtained will be consistently higher than those obtained by either direct aminolysis of sulfinyl chloride or deamination of sulfamide. The direct aminolysis of sulfuryl chloride does not work well with aromatic amines, for which ring chlorination is a complication. 

Carbon-nitrogen systems (alipbnuc and aromatic amines includes N-deolkylution. oxidative deamination, N-oxidc formation. N-hydroxylation)... 

The relationship of MAO and MPTP has neurobiological relevance beyond MPTP neurotoxicity. Types A and B MAO catalyze the a-carbon oxidative deamination of monoamine neurotransmitters and other aromatic amines. These genetically dissimilar isozymes show differential selectivity for specific substrates and inhibitors (63). Most intraneuro-nal MAO is mitochondrial and type A, and oxidizes primary amines to aldehydes, which are then converted by aldehyde reductases to alcohols or carboxylic acids, including dihy-droxyphenylatic acid (DOPAC) from DA Additional 3-0-methylation yields the majorfmal human metabolite of DA, homovanillic acid (HVA see Fig. 12.4). 

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