Phenols from arylamines

Arylamines are converted by diazotization with nitrous acid into arenediazonium salts, ArN2+ X-. The diazonio group can then be replaced by many other substituents in the Sandmeyer reaction to give a wide variety of substituted aromatic compounds. Aryl chlorides, bromides, iodides, and nitriles can be prepared from arenediazonium salts, as can arenes and phenols. In addition to their reactivity toward substitution reactions, diazonium salts undergo coupling with phenols and arylamines to give brightly colored azo dyes. 

Aryldiazonium salts, usually obtained from arylamines, undergo replacement of the diazonium group with a variety of nucleophiles to provide advantageous methods for producing aryl halides, cyanides, phenols and arenes by reductive removal of the diazo group. Coupling reaction of aryldiazonium salts with phenols or arylamines give rise to the formation of azo dyes. 

In general, EC reactions are typically observed according to the following general rank order (by relative ease of oxidation) o,p-quinol and o,p-aminophenol > tertiary amine > m-quinol rv phenol rv arylamine > secondary amine thiol > thioether primary amines, aliphatic alcohols. (HDVs) each redox active metabolite are obtained from the response across adjacent EC-Array sensors. These data are a reflection of the kinetic and thermodynamic components of electron transfer reactions. Since chemical structure is a critical determinant of an analyte s redox behavior, the intrinsic generation of an HDV with EC-Array provides qualitative information for each species. 

Tricyanovinyl-N,N-dimethylaniline has been prepared by adding hydrogen cyanide to -dimethylaminobenzalmalono-nitrile and oxidizing the adduct.3 The present procedure, an adaptation of one that has been published,3 is the more convenient preparative method. It can be applied to a wide variety of secondary and tertiary aromatic amines to give />-tricyanovinyl-arylamines that, like the present one, are dyes.3 Other types of aromatic compounds also condense with tetracyanoethylene in this manner. Thus one can obtain 4-tricyano vinyl-2,6-dimethyl-phenol from 2,6-dimethylphenol, 2-tricyanovinylpyrrole from pyrrole, and 9-tricyanovinylphenanthrene from phenanthrene.4... 

Phenols may be prepared by diazotization of the corresponding aniline derivative. The problem simplifies itself, therefore, to the preparation of m-bromoaniline. Recognizing that arylamines are ultimately derived from nitroarenes, we derive the retrosynthetic sequence of intermediates ... 

Although several peroxidase enzymes obtained from plant, animal, and microbial sources have been investigated for their ability to catalyze the removal of aromatic compounds from wastewaters, the majority of studies have focused on using HRP. In particular, it has been shown HRP can transform phenol, chlorophenols, methoxyphenols, methylphenols, amino-phenols, resorcinols, and various binuclear phenols [7], HRP was also used for the treatment of contaminants including anilines, hydroxyquinoline, and arylamine carcinogens such as benzidines and naphthylamines [7,8]. In addition, it has been shown that HRP has the ability to induce the formation of mixed polymers resulting in the removal of some compounds that are either poorly acted upon or not directly acted upon by peroxidase [7], This phenomenon, termed coprecipitation or copolymerization, has important practical implications for wastewaters that usually contain many different pollutants. This principle was demonstrated when it was observed that polychlorinated biphenyls (PCBs) could be removed from solution through coprecipitation with phenols [20]. However, this particular application of HRP does not appear to have been pursued in any subsequent research. 

Salts of primary aromatic amines react with nitrous acid to produce diazonium salts. The reaction is usually performed by adding a cold solution of sodium nitrite to a cold solution of the arylamine in aqueous mineral acid. The end point of the reaction is conveniently determined by the detection of excess nitrous acid with potassium iodide-starch paper. Sulfamic acid has long been used both in industry and in the laboratory to remove excess nitrous acid. It has been found to react with the more active diazo compounds. In most cases, high temperatures are avoided to prevent the formation of phenols and the decomposition of the unstable nitrous acid. An excess of mineral acid is necessary to prevent coupling between the diazonium salt and unreacted amine (cf. method 494). If the amine salt is somewhat insoluble, a fine crystalline form, which is produced by rapid crystallization from a warm aqueous solution, may be employed. ... 

Acid-catalyzed reactions of the phenol esters resulting in the formation of phenolic ketones are known as Fries rearrangements. Aluminum chloride was the first catalyst used but other Lewis acids are also effective. Examples from the recent literature are shown in equations (44) to (48). A nitrogen analog, that is the rearrangement of an acyl derivative of an arylamine, is shown in equation (49). Photo-Fries rearrangement reactions have also been studied in detail and are exemplified in equations (50) to (55). 

Hence the heterocycle can be used for the conversion of phenols into the corresponding primary arylamines [164], i.e. Ar-OH —> Ar-NH2. The chloroquinazoline 30 is obtained from anthranilic acid and benzamide ... 

On account of the facile amination of triflates, arylamines 31 can now be prepared from phenols 29 via their triflates 30. It should be added that electron-deficient aryl triflates 32 can be aminated without a catalyst [31,32]. 

A number of substrate-specific enzymes catalyze the transfer of SO4" from PAPS to specific acceptors such as phenols (47), chondroitin (60), and dehydroandrosterone (61). There is some indication that the incorporation of SO 4 into heparin proceeds by a similar mechanism (6 ). Further enzymic reactions which result in a transfer of SO4 into organic molecules are the sulfonation of choline by molds (63), and of arylamines to form arylsulfamates by liver homogenates (64). 

Hydrogen bonding in the lowest excited singlet states occasionally results in a decrease in fluorescence quantum yield upon going from hydrocarbon to hydrogen bonding solvents. Many arylamines and phenolic compounds demonstrate this behaviour which is due to internal conversion enhanced by coupling of the vibrations of the molecule of interest to those of the solvent. 

---