Amino phenols from hydroxyl amines

Phenols.—The ring hydroxyl compounds take the class name of phenols from the simplest member, hydroxy benzene or phenol. These are true aromatic compounds and in methods of formation, reactions and properties are distinctly different from aliphatic hydroxyl compounds or alcohols. Their outstanding distinction is their marked acid character, the alcohols being neutral (p. 103). This is attributed to the influence of the phenyl radical (CeHs—). The same influence is present in the amino derivatives, for the ring amines, CeHs— NH2, /CH3... 

By far the most stable nitroso compounds are those of the aromatic series. The smoothest C-nitrosation is achieved with phenols and tertiary amines having a free para-position. In benzene derivatives the nitroso group enters almost exclusively284 the para-position to the hydroxyl or amino group. In the naphthalene series the reaction is not always unidirectional 1-nitroso-2-naphthol is obtained almost quantitatively from 2-naphthol,285 but 1-naph-thol gives a mixture of about equal parts of 2- and 4-nitroso-l-naphthol.286... 

Any radical that may be converted to an amino group is capable of replacement by hydrogen. In certain instances such an indirect procedure may be of value. Since polynuclear phenols are transformed into amines by the Bucherer reaction,138 it has recently been suggested that the preparation of condensed ring hydrocarbons from the hydroxyl derivatives might best be achieved through the amines, rather than by the customary zinc dust fusion.189... 

Allyl chloroformate was used to protect both the phenolic hydroxyl and the amine of a series of amino acids (85-98% yield) with the aim of using a single protective group that was readily cleaved from the phenol (20% piperidine/DMF) but retained on the amine. Many of the Pd based methods discussed in the alcohol section should be applicable. 

CH3I, CH3OH, KHCO3, 20°C, 24h, 85-95% yield. These salts are generally used to protect tertiary amines during oxidation reactions. The conditions cited above form quaternary salts from primary, secondary, or tertiary amines, including amino acids, in the presence of hydroxyl or phenol groups. ... 

Nitro groups also increase the reactivity of phenols, but replacement of the hydroxyl by an amino group still needs temperatures of 150-200° and thus usually the use of pressure vessels.1054 Primary amines can be obtained at normal pressures from di- and tri-nitrated phenols and naphthols by melting them with urea 1055 1056 picramide, m.p. 188°, for instance, was formed in 88% yield by heating picric acid with 3 equivalents of urea at 173° for 36 h.1056... 

The presence of hydroxyl ions from the dissociation of ammonium hydroxide, alkyl or arylammonium hydroxide, or water is responsible for the simultaneous formation of hydroxy compounds in certain reactions. Thus, in the amination of chlorobenzene and chloroanthraquinones by this unit process, phenol and hydroxyanthraquinones, respectively, are found accompanying the amino compounds in the reaction product ... 

Although water hydrolyses acetic anhydride, amino groups and phenolic hydroxyls react much faster, and can therefore be acetylated in aqueous solution. This is the basis of the Schotten-Baumann conditions the reaction is driven by addition of sodium bicarbonate to remove the acid formed. The stirred aqueous solution of amines (or amine extract from tissues or biological fluids), totalling 4 ml, is treated with acetic anhydride (0.3 ml). A slight molar excess of sodium bicarbonate is added in small portions, letting effervescence subside each time. At the end of the reaction the products are extracted with dichloromethane (2x5 ml), and the combined extracts are blown down in a stream of nitrogen [25-27]. Similar procedures have been described for phenols [28, 29]. 

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