Acetic acid with arylamines

Primary amides are converted by treatment with lead tetraacetate in acetic acid into arylamines 701 an acyl nitrene is suggested as the intermediate. 

The Pd°-catalyzed arylations using arenediazonium tetrafluoroborates are limited to those diazonium salts that can be manipulated at room temperature. The reaction can, if necessary, be performed at temperatures up to 50 °C by using a mixture of an arylamine and tert-butyl nitrite in chloroacetic acid or in a mixture of chloroacetic and acetic acid (Kikukawa et al., 1981a). Styrene reacted with fourteen arylamines in the presence of 5 mol-% Pd(dba)2 to give the corresponding substituted stilbenes in yields of 46-97%. It is important for good yields to carry out these reactions in an acidic system. Without acid the yield was low (11%), and diazo tars were also formed. 

Aromatic nitroso compounds combine with primary arylamines in glacial acetic acid... 

A series of 3-substituted 2-nitrosiminobenzothiazohnes (35a-e) as well as the disub-stituted analog 35f were prepared (Scheme 3.24) [198]. The reaction of an arylamine hydrochloride with potassium thiocyanate gave the corresponding unsymmetrical thiourea [199]. Oxidative cyclizations with bromine provide the iminobenzothia-zolines [191, 200], which on treatment with sodium nitrite in acetic acid afforded the nitrosiminobenzothiazoline (35a-f). The nitrosiminobenzoselenazoline (42) was similarly prepared. 

The Sandoz company used the dibromoterephthalic acid method. This acid was made from p-xylcnc by brominating it to form 2,5-dibromo-p-xylene and then oxidising this to 2,5-dibromoterephthalic acid. Reaction of one mole of this acid with two moles of an arylamine in the presence of copper(II) acetate gives 2,5-bis(arylamino)terephthalic acid, which can be ring-closed to a linear quinacridone. Unsymmetrical substitution using two different arylamines is possible. 

The reagent prepared from the reaction of 30 % hydrogen peroxide with glacial acetic acid also contains peroxyacetic acid but the main product of arylamine oxidation is usually the corresponding nitroso compound. On heating with an excess of this reagent the nitro compound is usually obtained. ... 

Aromatic nitroso compounds combine with primary arylamines in glacial acetic acid to give symmetrical or unsymmetrical azo compounds (the Mills reaction).554 A wide variety of substituents may be present in both aryl groups. Unsymmetrical azo compounds have also been prepared by the reaction between aromatic nitro compounds ArN02 and N-acyl aromatic amines Ar NHAc.555 The use of phase transfer catalysis increased the yields. 

Palladium(II) salts apparently oxidize arylamines to arylpalladium salts since alkenes are arylated by reaction with only an aromatic amine and a palladium salt. However, yields are generally low.100 Much better yields are obtained if /-butyl nitrite is added and, of course, this forms the diazonium salt in situ. This not only saves a step but some diazonium salts which are too unstable to be isolated may be used as well. The reactions are carried out in the presence of acetic or chloroacetic acid with 5-10% bis(di-benzylideneacetone)palladium as catalyst (equation 41).101... 

Efficient synthetic methods have been developed for the synthesis of 4-functionalized quinolines mediated by triflic acid.703 Electron-rich, highly reactive ethynyl ketene-S,5-acetals react readily with arylamines and aldehydes in an aza-Diels-Alder reaction to afford the desired products [Eq. (5.256)]. Arylimines and ethynyl ketene-S,5-acetals react similarly (60-70% yields). 

The purification of sirupy ribose has in the past usually been carried out through the p-bromophenylhydrazone,1 7 27 a costly and laborious procedure. Recent studies of the arylamine ribosides have resulted in the discovery of a cheaper and more convenient method for the purification of ribose.28 29 30 The procedure is based upon the fact that ribose, dissolved in aqueous alcohol containing an arylamine such as aniline and an alkali metal salt such as sodium sulfate and having a pH of 4, is precipitated in high yield as a crystalline arylamine riboside-salt complex. The arylamine riboside may be extracted from this complex with dioxane and decomposed by boiling in water containing a trace of acetic acid. After the arylamine has been removed by steam distillation or through formation of a Schiff base with formaldehyde or benzaldehyde, the pure, crystalline ribose may be recovered. 

Tertiary arylamines were prepared in good yields by hydrogenation of an alcoholic solution of a nitro compound and an aldehyde over Raney Ni in the presence of triethy-lamine hydrochloride or, better, over platinum oxide in the presence of acetic acid (eq. 6.22).48 Base metal and platinum metal sulfides are also effective to the reductive alkylation of nitro compounds with ketones36,37 as in an example shown in eq. 6.23. 

Arylamines 79 are allowed to react under acidic conditions, in the presence of acetic acid, which affects even Ihe chemosclectivity of the reaction with formation of N-Mannich base when the molar ratio acid/sub.strate is very low (1 25). " ... 

Arylations. Copper(II) acetate catalyzes the reaction of arylboronic acids with phenols and amines (including imidazole and amides) to provide diaryl ethers (e.g., for synthesis of thyroxine) and arylamines, respectively. The reactions are quite erratic, although some preparatively useful cases have been found. 

Oxidation of arylamines, nitroso compounds, and azobenzenes. Several 2,6-di-haloanllines have been oxidized successfully to the nitroso compounds with 30% hydrogen peroxide in acetic acid at room temperature. When a solution of the reactants is let stand for a time, crystals of the (dimeric) nitroso compound begin to... 

The reactions of A-chloroalkylphosphazenes with hydroxylamine hydrochloride to give (73) proceed in a similar manner. Derivatives of (73) were obtained by reactions with arylamines, with sodium aryloxides, and with acetic (or formic) acid. The latter is noteworthy in that the proton of the hydroxy-group in (74) does not migrate to nitrogen. 

Oxidations of 2,2 -diaminobiphenyls with sodium perborate, phenyl iodosodiacetate, ° or manganese dioxide have given benzo[c]cinnolines with hydrogen peroxide in acetic acid, cyclization is accompanied by N-oxidation. These reactions, which parallel the oxidation of arylamines... 

Annulation of methylene and nitro groups of 2-arylaminomethyl-3-nitropy-ridine by heating with a primary arylamine in acetic acid leads to the pyrazolone together with a small amount of the corresponding pyrazole in some experiments. 

The triazenophosphorane (23.1) cyclizes when treated with a primary arylamine in acetic acid at room temperature. 

Secondary arylamines give products of attack at nitrogen as well as ring-substitution products. Thus, A -methylaniline reacts with formaldehyde and piperidine in the absence of acids to afford the aminal (6). In the presence of 0.5 mol equiv. of acetic acid the ring-substitution product (7) is obtained in 40% yield. Another type of aminal has also been obtained in reactions of secondary arylamines (V-ethyl-p-toluidine gives the important by-product (8) in a reaction with piperidine and formaldehyde. ... 

The condensation product of malononitrile with methyl cyanoacetate reacts with excess dimethylformamide dimethyl acetal at the amino as well as at the methylene group. The resulting compound cyclizes with arylamines to give l-aryl-4- [(A, JV-dimethylamino)methylene]-amino -2-oxo-l,2-dihydropyridine-3,5-dicarbonitriles which, in turn, with concentrated hydrochloric acid may be cyclized to furnish 6-aryl-4,7-dioxo-3,4,6,7-tetrahydropyrido[4,3-r/]-pyrimidine-8-carbonitriles 4.493... 

Azoxy compounds can also be obtained by oxidizing arylamines with peroxy compounds. Aniline is oxidized to azoxybenzene by hydrogen peroxide in acetonitrile-methanol at 50°, the yield being 62% 373 and 3,3 -dinitroazoxybenzene is obtained in 79% yield from m-nitroaniline and per-oxyacetic acid in glacial acetic acid.318... 

Aromatic nitroso compounds are known to react with primary arylamines in glacial acetic acid to produce symmetrical or unsymmetrical azo compounds (the Mill reaction). ... 

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