Ortho aminophenol

Shortly after Ingold received the preprint of the 1926 paper, he sent a paper to the Chemical Society which was published later in 1926. Here he dealt with the nitration of ortho aminophenol derivatives, adopting the kind of explanation that appeared in Robinson s paper and rationalizing the meaning of the so-called free and bound affinity, which he and Fliirscheim previously had been employing, by the new electronic interpretation. As discussed in chapter 8, the paper included Robinson s curved arrows but introduced a new delta (d) notation for polarity as well as other new terms. 126 The Manchester group referred to this paper as "Ingold s conversion." 127... 

On the other hand the ( )-isomer of deprenyl is a much more potent MAO-B inhibitor than the (+)-isomer. For these reasons racemic deprenyl has been replaced by ( )-deprenyl in clinical practice. In the racemic local anesthetic prilocaine (Figure 26.6) only the R-( )-isomer is metabolized to an aniline derivative (ortho-tolnidine) and to the corresponding para- and ortho-aminophenols that are highly toxic and responsible for met hemoglobinemia. ... 

N-tert-Butyl ortho-Aminophenol, ortho-Iminoquinone 93... 

The synthesis of some fluorine-containing polycyclic compounds involves intramolecular cyclization. Thus, heating quinoxalone, obtained by the reaction of the copper chelate of ethyl pentafluorobenzoylpyruvate with ortho-aminophenol in dimethylsulfoxide or DMSO-NEt3 leads to the product of intramolecular... 

Polyfluoro-2,3-epoxyalkanes are a convenient building block for the construction of heterocyclic systems. Nucleophilic attack on the central carbon of the epoxide ring of polyfluoro-2,3-epoxyalkanes gives rise to amides or ethers of the corresponding acids. Further reaction of a second nucleophile with the C = O may follow. So, ortho-aminophenole and polyfluoro-2,3-epoxypropane in the presence triethylamine give 2-(pentafluoroethyl)benzoxazole (90IZV2338) (Scheme 181). 

The more modern style of Skraup synthesis is used to make 8-quinolinol or oxine. ortho-Aminophenol has only one free position ortho to the amino group and is very nucleophilic, so acrolein can be used in weak acid with only a trace of strong add. Iron(lll) is the oxidant, with a bit of boric acid for luck, and the yield is excellent. 

Imines formed from trifluoromethylaryl ketones with ort/io-diamines or ortho-aminophenols undergo intramolecular cyclization, under basic conditions, with elimination of the CF3 group to give 2-arylbenzimidazoles and 2-aryloxazoles, respectively. The nature of the formal displacement process has been defined. 

Almost all syntheses of fluoroalkylated benzoxazoles are based on the use of ortho-aminophenols. Thus, condensation of perfluoroalkanoic acid imidates with o-aminophenol is a convenient method for preparation of 2-perfluoroalky 1-substituted benzoxazoles. 2-Trifluoromethyl- and 2-(perfluoropropyl)benzoxazoles can be synthesized by heating at 100 °C in dry dioxane, but the yield of benzoxazoles does not exceed 35 0 %. The best results are obtained by reaction of o-aminophenol with... 

In ortho aminophenols, acyl groups may rnigrahi from tlie oxygen to the nitrogen atom. 

Saloutin VI, Perevalov SG, Skryabina ZE (1996) Ethyl (pentafluorobenzoyl)pymvate and its derivatives in the reactions with ortho-aminophenol. Zhurn Oigan Khim 32 1386-1389... 

Nadeau, L.J., H.R. Luckarift, and J.C. Spain, December 2011. Biocatalytic process for the production of ortho-aminophenols from chloramphenicol and analogs. US patent 8071340. 

Figure 24. Speculation on a mechanism for the conversion of arylhydroxylamine compounds to the ortho-aminophenols.

N-substituted phenylhydroxylamine derivatives, e.g. N-acetyl and N-sulphonic acid, also form the para-aminophenol", but more bulky groups prevent reaction, it is thought by steric hindrance to the approach of the hydronium ion. -substituted phenylhydroxylamines, on the other hand form only the ortho product, it is thought via an intramolecular rearrangement, e.g. 

The Dimroth-Reichardt betaines are synthesized by reactions of p-aminophenols with pyrylium salts bearing aryl substituents in ortho position. 

Diozo Oxides. Diazo oxides are obtd irom substituted aminophenols amino-naphthols. They are also obtd from amino-phenolcarboxylic acids with the amino group either ortho or para to the hydroxyl group. 

When pentafluororutrobenzene reacts with ortho- or para-aminophenol in dimethylformamide solution containing sodium hydroxide, the 4-fluonne is replaced. Either the amino or the hydroxyl function of the aminophenol can act as the nucleophile depending on the reaction conditions [67] (equation 35)... 

Mononitrobenzylidene aminophenol, 02N.CgH4.CH -N.CgH4.0H mw 242.23, N 11.57%. The nine possible isomers of 2,3 or 4-Mononitrobenzylidene-amino-phenol with the substituted mononitroderiv in ortho(or 2)-, meta(or 3)-, and para(or 4> positions with respect to the hydroxy group of phenol, have all been prepd and described in the literature... 

The action of nitric acid on diacetylated p-aminophenol yields a dinitro derivative for which four structures are possible. Hydrolysis followed by deamination gives the known 3,5-dinitrophenol, thus proving that substitution occurs ortho to the acylated amino group.141... 

Hydroxylation of arylamines with persulfate ion, or Boyland-Sims oxidation, gives ortho-substituted aminophenols in good yields [29]. As with the Elbs oxidation, the procedure is also carried out in two steps - first, treatment with the oxidant to obtain an aminophenyl sulfate ester and, second, hydrolysis to obtain the final product. Primary, secondary and tertiary amines can all be used in this reaction. The ortho product is formed, except when no ortho-positions are available, which leads to para-substitution. Electrophilic attack on the ipso-carbon is believed to be the most likely mechanism, although minor radical pathways also seem to be present. 

Formulas 1,2-Benzenediamine, ortho-Diaminobenzene, para-aminophenol hydrochloride. Appearance White to brownish-yellow crystals. 

The formylation of phenols with the electron-rich olefin to give imidazolidin-2-yl-phenols is very selective and avoids mixtures of o- and p-isomers which are frequently obtained by methods commonly employed for the synthesis of phenolaldehydes. Para substitution of the cyclic aminal group in the phenol is preferred. If the p-position is blocked or sterically hindered, the reaction proceeds via the ortho- aminals to salicylaldehydes. Incorporation of more than one aldehyde group in the benzene nucleus is often achieved with hydroxy- and aminophenols. 

The reactivity of i satin derivatives towards o/T/io-aminophenol and ortho-aminothiophenol has been the subject of a number of reports and some of the products obtained are quite intriguing. The first report attests that 1-acetylisatin reacts with o-aminophenol to furnish a ring opened product in ethanol as well as in AcOH. The same result occurred with o-aminothiophenol in acetic acid, whilst in ethanol two different products were formed in a disproportionation reaction, as can be inferred from the change of the oxidation state of what was the 1-acetyli satin C-3 ketone group. The structures were assigned based upon spectroscopic data and, for the benzothiazole derivative, on comparison with a sample... 

Certain nuclear substituents ortho to a newly formed diazonium group may interact to form a cyclic structure with or without retention of the nitrogen atoms. Such is the case in the diazotization of o-phenylene-diamine in aqueous solution, the product being 1,2,3-benzotriazole (81%). If the ortho substituent is an activated methyl group, an indazole is formed. Hydroxyl groups ortho or para to the diazonium group may interact to form internal condensation products called diazo oxides. These compounds may also form in the reaction of halo- and nitro-substituted aminophenols. 

Such oxidations are especially easy, if electron-releasing groups such as hydroxyls or amino groups are located in para or ortho positions with respect to the amino groups. 3-Chloro-4-aminophenol stirred with sodium dichromate and sulfuric acid at a temperature below 35 °C gives a 58-63% yield of chloro-p-benzoquinone after the reaction mixture is allowed to stand at room temperature for 1 h [6J7]. Aminothymol is converted into thymoquinone on warming for 30 min with dilute sulfuric acid and sodium nitrite (equation 530) [451],... 

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