Chemical trapping experiments support a cation-radical mechanism for the oxidative polymerization of aniline

The oxidative polymerization of aniline in aqueous acidic solution was carried out in the presence of a variety of organic compounds as potential traps for postulated intermediates. The polymerization was inhibited by hindered phenols and electron-rich alkenes, traps for cation-radicals. However, polyaniline was still obtained in the presence of electron-rich arenes, such as 1,3-dimethoxybenzene and 1,4-dimethoxybenzene, known as excellent receptors of nitrenium ions. Polymerization of N-phenyl-1,4-phenylenediamine was similarly carried out in the presence of potential traps. Polyaniline containing an N-phenyl group was obtained in the presence of 1,3-dimethoxybenzene and 1,4-dimethoxybenzene. Hindered phenols and 4-methoxystyrene only slightly inhibited polymerization of N-phenyl-1,4-phenylenediamine which most probably proceeded by way of the stable diarylamino radical. Copolymerization of aniline with 10 wt % of N-phenyl-1,4-phenylenediamine in the presence of these traps gave similar results to the polymerization of pure aniline. These results have led to the proposed cation-radical polymerization mechanism of aniline, in which the polymerization is a chain growth reaction through the combination of a polymeric cation-radical and an anilinium cation-radical. Step growth character is also present when a polymeric aminium cation-radical end combines with a diarylaminoended polymer. The copolymerization of N-phenyl-p-phenylenediamine can also occur by reaction of aniline cation-radical with a polyarylamine radical. The nitrenium mechanism was further rejected by the fact that attempted polymerization of N-phenylhydroxylamine, which forms authentic nitrenium ions in acid, failed to give polymer. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2569–2579, 1999     

Carbonylation of nitrobenzene in methanol with palladium bidentate phosphane complexes: an unexpectedly complex network of catalytic reactions, centred around a Pd-imido intermediate

The reactivity of palladium complexes of bidentate diaryl phosphane ligands (P₂) was studied in the reaction of nitrobenzene with CO in methanol. Careful analysis of the reaction mixtures revealed that, besides the frequently reported reduction products of nitrobenzene [methyl phenyl carbamate (MPC), N,N′‐diphenylurea (DPU), aniline, azobenzene (Azo) and azoxybenzene (Azoxy)], large quantities of oxidation products of methanol were co‐produced (dimethyl carbonate (DMC), dimethyl oxalate (DMO), methyl formate (MF), H₂O, and CO). From these observations, it is concluded that several catalytic processes operate simultaneously, and are coupled via common catalytic intermediates. Starting from a P₂Pd⁰ compound formed in situ, oxidation to a palladium imido compound P₂Pd^II?NPh, can be achieved by de‐oxygenation of nitrobenzene 1) with two molecules of CO, 2) with two molecules of CO and the acidic protons of two methanol molecules, or 3) with all four hydrogen atoms of one methanol molecule. Reduction of P₂Pd^II?NPh to P₂Pd⁰ makes the overall process catalytic, while at the same time forming Azo(xy), MPC, DPU and aniline. It is proposed that the Pd–imido species is the central key intermediate that can link together all reduction products of nitrobenzene and all oxidation products of methanol in one unified mechanistic scheme. The relative occurrence of the various catalytic processes is shown to be dependent on the characteristics of the catalysts, as imposed by the ligand structure.     

Synthesis and characterization of some new aromatic diamine monomers from oxidative coupling of anilines and substituted aniline with 4-amino-N,N-dimethyl aniline

New aromatic diamine monomers prepared from condensation reactions of aniline, p-chloroaniline, p-nitro aniline, p-chloro-m-nitro aniline with 4-amino-N,N-dimethylaniline (2:1) (aniline:reagent) in the presence of potassium dichromate in acidic media yielded new monomers of a highly colored violet and reddish-violet. Mechanism of the reaction of aniline with 4-amino-N,N-dimethylaniline in the presence of potassium dichromate as an oxidant is expected to proceed through nucleophilic substitution reaction, and the mechanism proceeds facilitated a nucleophilic attack of the substituted aniline ring on the –NH₂ group of the reagent; through partial protonation of their –NH₂ group, forming in diamine dye and their identification was confirmed by IR, ¹H NMR, and CHN analyses.     

Copper-Mediated monochlorination of anilines and nitrogen-containing heterocycles

A simple and selective copper(II) chloride-mediated monochlorination of anilines and nitrogen-containing heterocycles has been developed. Stirring a mixture of aniline, copper(II) chloride, lithium chloride in EtOH under reflux condition produced 4-chloroaniline with high yield. Eighteen substrates including substituted anilines, N-substituted anilines, N,N-disubstituted anilines, 5-nitroindole and carbazole were all reactive and afforded desired products in moderate to excellent yields (52%–98%).     

Reactions of tungsten(VI) and molybdenum(V) chlorides,and tungsten(VI) and molybdenum(VI) oxychlorides,with azoxybenzene

Reactions of W^VI and Mo^V chlorides with azoxybenzene yield ionic species of W^VI and Mo^VI oxychlorides in which the cation is a protonated azobenzene. The reaction between MoCl₅ or MoOCl₄ and azoxybenzene gives, after extraction with methylene chloride—ethanol mixture, the complex [trans-MoOCl₄(OC₂H₅)]^? [C₁₂H₁₀N₂H]⁺. In contrast, WOCl₄ reacts with azoxybenzene to give a stable non-ionic adduct in which the organic moiety is coordinated through its oxygen atom trans to the WO bond. Several complexes of substituted azoxybenzene having similar structures are described.     

Catalytic and electrocatalytic oxidation of aniline to nitrobenzene over vanadium silicate molecular sieves: VS-1 usingt-butyl hydroperoxide (TBHP) as oxidant

A comparison of the results of catalytic and electrocatalytic oxidation of aniline using VS-1 in the presence of H₂O₂ and TBHP indicates remarkable differences in conversion and selectivity. VS-1 catalyzes the oxidation of aniline selectively to nitrobenzene (73%) in the presence oft-butyl hydroperoxide (TBHP), while azoxybenzene (95.2%) is formed selectively when H₂O₂ is used. Cyclic voltammetric studies show a three-step oxidation of aniline to nitrobenzene in H₂O₂ but in the presence of TBHP only one step is observed. Electrocatalytic oxidation of aniline to nitrobenzene occurs at a potential 700 mV less than that corresponding to H₂O₂ as oxidant along with a selectivity of 91.8%. The enhancement of electrocatalytic rate is attributed to the stabilization of electron deficient transition state.     

Synthesis and reactions of thiosemicarbazides, triazoles, and Schiff bases as antihypertensive α-blocking agents

Methyl 2-(thiazol-2-ylcarbamoyl)acetate was synthesized and used as starting material. It was treated with hydrazine hydrate to afford the hydrazide, which was reacted with nitromethane and formaldehyde to give the saturated nitropyrimidine. The hydrazide was reacted with phenyl isothiocyanate to afford the thiosemicarbazide, which was cyclized with ethyl bromoacetate, sodium hydroxide, or sulfuric acid to afford N-phenylthiazolidinone, N-phenyltriazole, and thiadiazolyl derivatives. The methyl 2-(thiazol-2-ylcarbamoyl)acetate was coupled with diazonium salts of aniline, 4-chloroaniline, 4-bromoaniline, or 4-aminobenzenesulfonamide to afford the carbamoyl acetates, which were reacted with 2-aminobenzimidazole, 1,2,4,5-tetrachlorophthalic anhydride, and hydrazine hydrate to afford the corresponding thiazolylmalonamide, tetrachloroisoindolylimide, and tri-azole derivatives. Schiff bases and imides are newly synthesized candidates obtained via simple condensation of the hydrazide with aldehydes, 2,3-pyridinedicarboxylic anhydride, or 1,8-naphthalenedicarboxylic anhydride. The pharmacological screening showed that many of these compounds have good antihypertensive α-blocking activity and low toxicity.     

N‐phenyl‐substituted pyrrolidines,piperidines and azabicyclics by a tandem reduction‐double reductive amination reaction

N‐Phenyl‐substituted pyrrolidines and piperidines have been synthesized by catalytic reduction of nitrobenzene in the presence of 4‐ and 5‐oxoaldehydes, respectively. The process involves reduction of the aromatic nitro group to give the N‐phenylhydroxylamine or aniline followed by reductive amination with the two carbonyl functional groups. Monocyclic systems are generally formed in high yield and are easily purified. The method has also been extended to the synthesis of fused N‐phenylazabicyclics from 2‐(3‐oxo‐propyl)cycloalkanones. A high degree of diastereoselectivity for the trans‐fused product is observed in substrates having an ester group α to the cycloalkanone carbonyl. Bicyclic precursors lacking this ester group give mixtures of cis and trans products. Finally, contrary to previous reports, we have demonstrated that aniline can be substituted for nitrobenzene in these reactions.     

Thermal degradation studies of substituted conducting polyanilines

The synthesis of conducting polymers based on m-nitroaniline, m-chloroaniline and m-aminophenol by aniline initiated ammonium peroxydisulfate oxidation, has been attempted. The IR spectra of the polymers have been studied. Thermogravimetric analysis of the conducting polymers has been followed using a computer analysis method LOTUS PACKAGE, developed by us for assigning the degradation mechanism. A number of equations have been used to evaluate the kinetic parameters. The mechanism of degradation of the conducting polymers has been explained on the basis of their kinetic parameters.     

Study of alkaloids from the flora of the Siberian and Altai regions. 5. Synthesis of new elatidine derivatives

Elatidam, elatidamic acid, and elatidal were obtained for the first time by oxidation of the diterpene alkaloid elatidine with KMnO₄ or CrO₃ and characterized. The reactions of elatidal with hydroxylamine, aniline, allylamine, and methyl glycinate afford the corresponding imines. Elatidal N-phenyl- and N-allylimines were reduced with NaBH₄ to give the corresponding diamines.     

A novel synthetic method to phenyl-capped penta- and hexaaniline

A new convenient method is reported for the synthesis of the phenyl-capped pentamer and hexamer of aniline. The method was accomplished by the reaction of the parent aniline tetramer in the pernigraniline oxidation state with diphenylamine and N-phenyl-1,4-phenylenediamine in the leucoemeraldine oxidation state, respectively. The mechanism probably involves the formation of cation radicals and their coupling.     

Metallextraktion mit N-thiobenzoyl-N-phenylhydroxylamin: Extraction of metal ions with N-thiobenzoyl-N-phenylhydroxylamine

The extraction parameters pH_{$\text{1}\text{2}$} and K_ex for Mn, Fe, Co, Ni, Cu, Zn, Cd, and Pb with N-thiobenzoyl-N-phenylhydroxylamine are reported. N-Thiobenzoyl-N-phenylhydroxylamine extracts metals from more strongly acidic solutions than does N-benzoyl-N-phenylhydroxylamine. Iron(III) is extracted as a 1:2 chelate with the extracant, whereas iron(II) forms the expected tris chelate by oxidation. The other bivalent ions are extracted as their bis chelates.     

Thermal equilibrium between “isoxazolidine” and “enamine”

Nitrones formed from the reaction of $\text{N}$-phenylhydroxylamine and aldehydes dimerized to isoxazolidines. A new thermal equilibrium between isoxazolidine and $\text{N}$-hydroxyenamine in DMSO was studied by ¹H and ¹³C NMR.     

Antipyrilquinoneimine dye formation by coupling aniline derivatives with 4-aminoantipyrine in the presence of ruthenium nanoparticles

The coupling of 4-aminoantipyrine (4-AAP) with aniline derivatives catalyzed by ruthenium nanoparticles (Rnp) has been studied by UV-Vis spectroscopy in aqueous medium. The rate constant for antipyrilquinoneimine dye formation depends on the nature of the aniline substituent and the pH, ionic strength and temperature of the reaction medium. The maximum rate constant of the dye formation reaction is observed at pH 3.6. Aniline derivatives with electron donating substituents show higher rate constant values than those with electron withdrawing substituents, with increasing rate constant values in the order: N,N-dimethyl aniline > o-toluidine > o-chloroaniline > m-chloroaniline. With pseudo first order kinetics, the total order is 1.0 + 1.0 + 1.0 = 3.0, which includes the orders with respect to amine, 4-AAP and Rnp. Studies on these effects help to complete the kinetic analysis as well as propose the reaction pathway. Furthermore, TEM measurement confirms that the nanoscalar size of the Rnp is 7 nm.     

Reactions of <Emphasis Type="Italic">N</Emphasis>-and <Emphasis Type="Italic">C</Emphasis>-Alkenylanilines: VII. Synthesis of Indole Heterocycles from Products of Reaction between <Emphasis Type="Italic">N</Emphasis>-Mesyl-2-(1-alken-1-yl)anilines and Halogens

N-Mesyl-2-(1-methyl-1-butenyl)-6-methylaniline reacted with Br₂ to afford N-mesyl-2-(3-bromo-1-penten-2-yl)aniline that under treatment with NH₃ or amines underwent cyclization into N-mesyl-7-methyl-3-methylene-2-ethylindoline. The reaction of N-mesyl-2-(1-methyl-1-buten-1-yl)-4-methyl- and 2-(1-methyl-1-buten-1-yl)aniline with Br₂ gave rise to the corresponding N-mesyl-2-(2-bromo-1-methyl-1-buten-1-yl)anilines. Under the similar conditions N-tosyl-2-(1-cyclohexen-1-yl)aniline was converted into N-tosyl-2-(6-bromo-1-cyclohexen-1-yl)aniline that under treatment with NH₃ furnished N-tosyl-1,2,3,9a-tetrahydrocarbazole. The reaction of N-mesyl-1,2,3,9a-tetrahydrocarbazole with CuBr₂ in MeOH afforded N-mesyl-4-methoxy-1,2,3,4-tetrahydrocarbazole. N-Mesyl-6-methyl-2-(1-cyclopenten-1-yl)aniline in reaction with Br₂ in the presence of NaHCO₃ was oxidized into the corresponding cyclopentenone, and with NBS it gave N-mesyl-2-(2-bromo-1-cyclopenten-1-yl)aniline.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 5, 2005, pp. 730–737.Original Russian Text Copyright © 2005 by Gataullin, Sotnikov, Spirikhin, Abdrakhmanov.     

Synthesis and reactions of thiosemicarbazides,triazoles, and <Emphasis Type="Italic">Schiff</Emphasis> bases as antihypertensive α-blocking agents

Methyl 2-(thiazol-2-ylcarbamoyl)acetate was synthesized and used as starting material. It was treated with hydrazine hydrate to afford the hydrazide, which was reacted with nitromethane and formaldehyde to give the saturated nitropyrimidine. The hydrazide was reacted with phenyl isothiocyanate to afford the thiosemicarbazide, which was cyclized with ethyl bromoacetate, sodium hydroxide, or sulfuric acid to afford N-phenylthiazolidinone, N-phenyltriazole, and thiadiazolyl derivatives. The methyl 2-(thiazol-2-ylcarbamoyl)acetate was coupled with diazonium salts of aniline, 4-chloroaniline, 4-bromoaniline, or 4-aminobenzenesulfonamide to afford the carbamoyl acetates, which were reacted with 2-aminobenzimidazole, 1,2,4,5-tetrachlorophthalic anhydride, and hydrazine hydrate to afford the corresponding thiazolylmalonamide, tetrachloroisoindolylimide, and tri-azole derivatives. Schiff bases and imides are newly synthesized candidates obtained via simple condensation of the hydrazide with aldehydes, 2,3-pyridinedicarboxylic anhydride, or 1,8-naphthalenedicarboxylic anhydride. The pharmacological screening showed that many of these compounds have good antihypertensive α-blocking activity and low toxicity. Correspondence: Abd El-Galil E. Amr, National Research Center, Applied Organic Chemistry, Dokki, Cairo, Egypt.     

Convenient preparative methods for N-aryl-γ-pyridones from γ-pyrones

2-Hydroxymethyl-5-methoxy-4-H-pyran-4-one ( 1 ) reacts with aniline and six aniline derivatives in very dilute aqueous hydrochloric acid at reflux temperature to give the N-aryl-γ-pyridone. A second procedure utilizes the aromatic amine hydrochloride by reacting it with 1 in aqueous medium at reflux temperature. p-Nitroaniline hydrochloride and 1 give the N-aryl-γ-pyridone in 65% yield, as opposed to 12% from the dilute acid procedure.     

Preparation of densely grafted poly(aniline‐2‐sulfonic acid‐co‐aniline)s as novel water‐soluble conducting copolymers

Various densely grafted polymers containing poly(aniline‐2‐sulfonic acid‐co‐aniline)s as side chains and polystyrene as the backbone were prepared. A styryl‐substituted aniline macromonomer, 4‐(4‐vinylbenzoxyl)(N‐tert‐butoxycarbonyl)phenylamine (4‐VBPA‐^tBOC), was first prepared by the reaction of 4‐aminophenol with the amino‐protecting moiety di‐tert‐butoxyldicarbonate, and this was followed by substitution with 4‐vinylbenzyl chloride. 4‐VBPA‐^tBOC thus obtained was homopolymerized with azobisisobutyronitrile as an initiator, and this was followed by deprotection with trifluoroacetic acid to generate poly[4‐(4‐vinylbenzoxyl)phenylamine] (PVBPA) with pendent amine moieties. Second, the copolymerization of aniline‐2‐sulfonic acid and aniline was carried out in the presence of PVBPA to generate densely grafted poly(aniline‐2‐sulfonic acid‐co‐aniline). Through the variation of the molar feed ratio of aniline‐2‐sulfonic acid to aniline, various densely grafted copolymers were generated with different aniline‐2‐sulfonic acid/aniline composition ratios along the side chains. The copolymers prepared with molar feed ratios greater than 1/2 were water‐soluble and had conductivities comparable to those of the linear copolymers. Furthermore, these copolymers could self‐dope in water through intermolecular or intramolecular interactions between the sulfonic acid moieties and imine nitrogens, and this generated large aggregates. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1090–1099, 2005     

REDUCTION OF NITROGEN FUNCTIONAL GROUPS WITH ELEMENTAL SULFUR IN LIQUID AMMONIA AND AMINES

Abstract

Nitrosobenzene and phenylhydroxylamine were reduced with elemental sulfur in liquid ammonia and amines to give aniline as the major product. Although hydrazobenzene was obtained by the reactions of azoxybenzene and azobenzene with elemental sulfur in liquid ammonia and amines, the expected aniline was not obtained. The utilities of elemental sulfur in liquid ammonia and amines as reductant is discussed.     

On-line microdialysis–high-performance liquid chromatographic determination of aniline and 2-chloroaniline in polymer industrial wastewater

Determination of aniline and 2-chloroaniline in polymer industrial wastewater was examined using high-performance liquid chromatography with on-line microdialysis. After dilution, aniline and 2-chloroaniline in the sample were diffused through a cellular dialysis membrane into the perfusion stream under controlled conditions. Conditions for obtaining optimum dialysis efficiency such as flow-rate and polarity modifier in the perfusion stream, pH and added salt in the sample solution, as well as chromatographic conditions were investigated. The results indicate that the dialysis achieved at a sample matrix pH value of 9.5 with 0.1 M NaCl addition, and the perfusate at 10-μl/min flow-rate offered optimum dialysis efficiency. The aniline and 2-chloroaniline were well separated in an acceptable time on a reversed-phase C₁₈ column eluted with 40% aqueous methanol solution at pH 7.0 and 1.0 ml/min flow-rate. The proposed method provided a very simple procedure to determine aniline and 2-chloroaniline in wastewater. Application was illustrated by the analysis of aniline and 2-chloroaniline in wastewater released from a polymer factory.