Oxidation of substituted anilines

Klausen, J., S. B. Haderlein, and R. P. Schwarzenbach, Oxidation of substituted anilines by aqueous MnOz Effect of cosolutes on initial and quasi-steady-state kinetics , Environ. Sci. Technol., 31, 2642-2649 (1997). 

First-order dependence is observed with respect to both the oxidant and reductant in the oxidation of substituted anilines with peroxomonosulfate anion. Addition of acid causes retardation of the reaction. Yukawa-Tsuno correlation of the rates gave a negative reaction constant (p -1.7) and analysis of the effect of solvent in terms of Grunwald-Winstein equation (m 0.4) indicated an S -type reaction. 

Hilmi, A., Luong, J. H. T., and Nguyen, A. L., Capillary elecrophores applied to kinetic studies of photocatalitic oxidation of substituted anilines. Chromosphere, 36, 3137-3147, 1998. 

Oxidation of Substituted Anilines with Urea-Hydrogen Peroxide in Glacial Acetic Acid... 

Vanadium complexes and in particular [VO(acac)2] are the most active catalysts for the oxidation of substituted anilines to nitro compounds. The effect of substituents upon reaction rate corresponds to a reaction involving an electron deficient transition state in that electron withdrawing groups decrease the rate and vice versa. The relative order of reactivity p-Me > m-Me > aniline > p-Cl > p-Br > m-Cl > m-Br is the same as observed in electrophilic aromatic substitution. Straight line correlations between the log of the relative rates and Hammett a or Brown constants were obtained with p values of— 1.42 and — 1.97, respectively, indicating an electron deficient transition state in the rate determining step. 

Ibne-Rasa and Edwards have recently studied the peracetic add oxidation of substituted anilines and some of their conclusions bear on the mechanism of peroxidic oxidations of amines in general. The reaction rates have a first-order dependence on the concentrations of unprotonated amine and peracetic add (equation 78) and the Ham-... 

The MCC oxidation of substituted anilines in ACOH-H2O to corresponding azobenzenes is fractional order in substrates and H+ ions. The rates are retarded by electron-withdrawing substituents and enhanced by electron-releasing substituents. The PPCC oxidation of a-hydroxy acids in the same solvent is fractional order in H" " ion and the rates increase with decrease in dielectric constant. The order of the reactivity is mandelic > lactic > glycolic acid. ... 

Rate retardation with increasing H" ions in the meso-tetraphenyl-porphyriniron(III) chloride-catalysed oxidation of substituted aniline by oxone in ACOH-H2O has been ascribed to the increasing concentration of less reactive protonated aniline species. The oxidation complied with the isokinetic relationship but no linear free energy relationships were found the solvent interaction had a role in the reactivity." ... 

NOL-based systems for addition of (substituted) anilines to meso epoxides. Hou found that a ytterbium-BI NO L complex catalyzed desymmetrization of cyclohexene oxide in up to 80% ee [15], Shibasaki demonstrated that a praseodymium-BINOL complex could promote addition of p-anisidine to several epoxides in moderate yields with modest enantioselectivities (Scheme 7.7) [16]. 

With respect to the kinetics of oxidation reactions, the same comments as made in Section 14.2 are, of course, valid. To illustrate, we consider the oxidation of substituted phenols and anilines by Mn02 and of substituted phenols by HC1O4. By analogy to the type of LFER used to evaluate NAC reduction (Eq. 14-38), we can relate oxidation reaction rates to the one-electron standard oxidation potentials of... 

As an example, we consider the oxidation of a series of monosubstituted anilines by Mn02 in batch systems. In this case, quite a good correlation between log kK (expressed relative to R of 4-chloroaniline) and E]/2(ArX ) is obtained (Fig. 14.20). The slope of -0.54 indicates that, similar to what we have postulated for the reduction of NACs by surface-bound Fe(II) (see Fig. 14.10 /), the overall reaction rate is determined not solely by the actual electron transfer but also by other steps such as precursor complex formation. Comparable results (slopes of between-0.5 and -0.6) were obtained for the reaction of Mn02 at pH 4 with a series of substituted anilines (Laha and Luthy, 1990), and with a series of substituted phenols at pH 4.4 (Stone, 1987). In all these cases, only initial pseudo-first-order rate constants determined with clean Mn02 were considered. In the presence of solutes such as Mn2+ that may adsorb to the oxide surface, much slower reaction rates and much... 

Because substituted anilines are widely available, they are ideal starting materials for the synthesis of indoles. Although anilines are often the precursors of the hydrazones used in the Fischer cyclization, more direct methods for conversion of anilines to indoles would be highly desirable. Such a process would, in general, have to involve some method for specific o -substitution of the aniline derivative. In the most successful method of this type which has been developed to date, a specific rearrangement effecting o-substitution is the key to a synthetic scheme which constructs indoles from anilines via anilinosulfonium ions. The procedure, which in appropriate circumstances can be carried out without isolation of the intermediates, involves oxidation of the aniline to an A-chloroaniline, reaction with a thiomethylmethyl ketone and a weak base, followed by cyclizative condensation (equation... 

The oxidation of substituted aromatic amines with silver(l) carbonate on Celite has been shown to yield symmetrically substituted phenazines, albeit in poor yields. 2,7-Dimethoxy-hexafluorophenazine has been obtained upon electrolysis of solutions of 4-methoxytetrafluoro-aniline, and oxidative coupling of benzene-1,4-diamine with aniline or substituted anilines also gives phenazine derivatives. ... 

Simulation of biosynthesis of phenazine pigments through the dimerization of substituted anilines by symmetrical carbon carbon pairing leads to substituted phenazines. Thus, oxidation of anthranilic acid with manganese(IV) oxide or lead(IV) oxide affords phenazine-l,6-di-carboxylic acid in 16% yield. ... 

In this review, attention is focused primarily on the oxidation mechanisms under the given conditions, which is the essential topic of interest for organic chemists. Reaction pathways will be outlined if they seem to be well established. However, even small differences in medium properties used by different researchers can lead to serious variations as will be shown in some examples. Anodic oxidation of unsubstituted aniline is discussed in Section II and electrode reactions of /V-substifilled and C-substituted anilines in Sections III and IV, respectively. In the last case, the oxidation of reactants with monosubstituted ring is presented first (para-substituents separately from the effects of ortho- and mefa-substituents), and next the oxidation of di- and trisubstituted anilines. In each part the processes in dipolar aprotic solvents, in particular in acetonitrile (ACN) and /V. /V-dimethylformamide (DMF), are compared with those proceeding in aqueous solutions, chiefly in commonly used acidic media. 

Treatment of (silox)3Tam ((32), Scheme 44) with PhNH2 resulted in oxidative addition of an N—H bond to afford the hydride (silox)3Ta(NHPh)(H). This in turn eliminated dihydrogen to form (silox)3Ta(NPh).152 In contrast, the same reaction with p-CF3-C6H4NH2 produced (silox)3-Ta(NH2)(C6H4-p-CF3) from oxidative addition of a C—N bond (Scheme 44).15 The competition between N-H and C-N activation was investigated for a variety of substituted anilines, with electron-withdrawing substituents found to favor C-N activation. 

Benzimidazole synthesis. Nair and Adams" found that the reagent oxidizes 2-substituted aniline derivatives of type (I) to benzimidazoles (2) under very mild conditions in yields of 60-90%, depending upon the substituents in the aromatic... 

Sodium bismuthate can depolymerize poly-l,4-phenylene oxides in benzene in the presence of substituted aniline to give the corresponding anils in good yield (Scheme 5.5) [73CC562],... 

Oxidative polymerization of substituted aniline monomers is frequently more difficult than that of aniline. A significant recent advance has therefore been the... 

Manganese dioxide was also reactive toward other electron-rich aromatic compounds such as anilines (Laha and Luthy, 1990). The order of reactivity of substituted anilines toward Mn02 (alkoxy > alkyl > Cl > -COOH > NO2) was that expected for other oxidizing agents. The reaction products were mainly azobenzenes (PhN-= NPh) and azoxybenzenes... 

There are several methods reported in the literature for the oxidation of aniline, which include (i) the use of MnOs to produce azobenzene, (ii) the use of aqueous peracids to oxidize ortho-substituted aniline to nitrobenzene, (iii) the use of aqueous peracids to oxidize non-substituted anilines to azo- and azoxybenzene, (iv) the use of anhydric peracids to produce the corresponding nitrobenzenes, and (v) the use of catalytic systems, such as t-BuOjH-MoCVI), V(V), or t-BuOjH-TiCIV), to produce nitrobenzene or azoxybenzene. 

A number of reports on transition metal-free formations of benzo [c] cinnolines emerged in 2014. Sythana and collaborators prepared benzo [c] cinnoline N-oxides via a single-electron transfer mechanism (Scheme 11) (14EJ0311). In the presence of potassium tert.-butoxide and an aptotic nonpolar solvent benzo [c] cinnoline N-oxides 18 were obtained in moderate-to-high yields from the reaction of substituted anilines with nitrobenzenes. Both electron-donating substituents and electron-withdrawing halo substituents were well tolerated. When the halo substituents were in the... 

However, if this same reaction is carried out in a venturi loop reactor, the order of magnitude large values of k a in the venturi section is likely to result in a situation such that Equation 2.6 is valid. Consequently, the mass transfer limitation can be eliminated when the venturi loop reactor replaces the stirred tank type. Thus, the reaction can achieve the maximum intrinsic rate or operate at the maximum possible capacity. This matter has been briefly discussed in Section 3.4.2.4 for Uquid-phase oxidation of substituted benzenes. The solved reactor design problem in Section 8.13 shows that this is indeed the case for catalytic hydrogenation of aniline to cyclohexylamine. 

Table 12.5 Oxidation potential of substituted aniline compounds...

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