HPLC post column derivatization of aromatic amines usingN-methyl-9-chloroacridinium triflate

An HPLC post column chemical derivatization procedure based on the interaction between an acridinium triflate and amines to form highly colored derivatives on-line is described for the determination of aromatic amines. Benzocaine and butesin, local anesthetic agents that contain the aromatic amine group, were used as model compounds. Reversed-phase HPLC conditions were developed for both the separation of analytes and the reaction between analytes and the acridinium triflate in the system. Three-dimensional knitted teflon shape coils and the internal diameter and length of the coils were important parameters in reducing band broadening and background noise.N-Methyl-9-chloroacridinium triflate was shown to be applicable to the determination of primary aromatic amines, selected secondary aromatic amines, hydrazides, and hydrazines. Application of the on-line chemical derivatization procedure to the analysis of pharmaceutical dosage forms containing procainamide (primary aromatic amine), isoniazid (hydrazide), and hydralazine (hydrazine) is also described.     

Synthesis of 3-hetaryl-4,5,6,7-tetrahydrobenzo[b]thiophenes

A novel efficient synthesis of 3-hetaryl-4,5,6,7-tetrahydrobenzo[b]thiophenes was achieved by the cyclocondensation of ethyl 2-amino-4,5,6,7-tetrahydrobenzo[6]thiophene-3-carboxylate with selected o-substituted aromatic amines or with alifatic, aromatic and heterocyclic acid hydrazides in the presence of polyphosphoric acid.     

Synthesis of homoallylic amines and acylhydrazides by tin powder‐promoted multicomponent one‐pot allylation reactions

An efficient process for the synthesis of homoallylic amines and N′‐homoallylic hydrazides is developed from the one‐pot reaction of carbonyl compounds, amines or N‐acylhydrazines, allyllic bromide and tin powder using water as solvent. N‐Acylhydrazines are found to be more reactive than amines in these processes. They can react not only with aldehydes but also with ketones to give the corresponding N′‐homoallylic hydrazides. Copyright © 2016 John Wiley & Sons, Ltd.     

Isoindole derivatives from o-diacylbenzenes and aromatic amines

o-Acetylbenzophenone produced yellow 1,2-diaryl-3-(aryliminomethyl)isoindole by the reaction with aromatic amines in the absence of acid. On the reaction of o-diacetylbenzene under the similar condition, three types of yellow products were obtained. The structures of these isoindole derivatives were determined and their formation mechanism was proposed.     

Structure of aromatic polyimides

With a view to understanding the structure of aromatic polyimide backbone, model compound N,N-bis(4-phenoxyphenyl)-1,2:4,5-benzenetetracarboxdiimide was synthesized by the condensation of pyromellitic dianhydride and 4-aminodiphenyl ether in solvent N,N-dimethylacetamide or N,N-dimethylformamide. Various side products formed during the reaction were isolated and identified by spectroscopical methods. This study reveals that the polymer backbone contains nearly 85% imide rings. The uncyclizable residues in the backbone are those derived by the chemical interaction of polymerization solvent or by the modification of intermediate orthoamido acid. The uncyclizable nature of the latter was explained in mass and infrared (IR) spectral studies. The role of the dipolar solvent appears to be vital to imidization.     

Hydrosilylation Of (Hetero)aromatic Aldimines in the Presence of a Pd(I) Complex

The reaction of triethylsilane with heterocyclic and aromatic azomethines, catalyzed by the [Pd(allyl)Cl]₂ complex, was studied. It was found that the reaction is affected by the nature of the functional groups in the aza and methine parts of the aldimine molecules, which were produced by the condensation of furan, thiophene, and benzene aldehydes with aniline and its derivatives. The reactivity of a series of imines is compared with their electronic and structural characteristics, determined by quantum-chemical methods. The corresponding furan, thiophene, and aromatic amines and also certain silylamines were synthesized.     

Aromatic polyamides. V. A general synthesis of polyamides from aromatic diacids and aromatic diamines in sulfur trioxide

The reaction of terephthalic acid (TA) and para-phenylenediamine sulfate (PPD-S) in sulfur trioxide to form anisotropic, sulfonated poly(p-phenyleneterephthalamide) (SPT) dopes was reported in Part IV of this series. We have found now that the TA/PPD-S polymerization is only one example of a more general polyamide condensation reaction of aromatic diamines and aromatic diacids. Sulfonation of the aromatic diamine ring during TA/PPD-S polymerization in SO₃ was a major side reaction. Sulfonation was reduced or eliminated by aromatic diamine ring substitution with unreactive substituents, particularly chlorine and fluorine. Polymerization of 2,3,5,6-tetrafluoro-phenylenediamine with TA in SO₃ at 80°C (18% concentration) produced unsulfonated poly(tetrafluoro-para-phenyleneterephthalamide) (F-PPT) with an inherent viscosity of 2.2. The halogenated, all-para aromatic polymers formed highly anisotropic (liquid crystalline) dopes. Monomers that formed polymers in which the chain bond angle deviated from 180° (e.g., meta-oriented monomers) yielded only isotropic polymer solutions. The mechanism and rate of diamine–diacid reactivity in SO₃ was related to diamine basicity. Whereas the less basic aromatic diamines (as sulfates) polymerized with aromatic diacids in SO₃, the more basic aliphatic diamines (as sulfates) would not. Aliphatic, cycloaliphatic, and aryl-aliphatic diacids were degraded by or reacted with the solvent (SO₃). Thermogravimetric analyses of F-PPT and monosulfonated poly(chloro-para-phenyleneterephthalamide) at 20°C/min showed weight loss only above 380 and 370°C, respectively.     

Synthesis of Novel Symmetric Porphyrin Schiff Base Dimers by Solid–Liquid Reaction Methodology

A new convenient solid–liquid condensation reaction procedure for the synthesis of novel asymmetric and symmetric meso‐tetraarylporphyrin and metalloporphyrin Schiff bases is reported. The condensation reaction between β‐formyl porphyrin or metalloporphyrins and aromatic amines was carried out at solid–liquid interface by using neutral alumina powder as a solid support for β‐formyl porphyrin or metalloporphyrins and absolute ethanol as the carrier solvent for aromatic amines. Six different asymmetric porphyrin/metalloporphyrin Schiff bases were synthesized via solid–liquid interface reaction methodology. The same solid–liquid synthetic methodology was applied for the synthesis of six novel symmetric Schiff base porphyrin/metalloporphyrin dimers. The comparison of UV–visible spectra of porphyrin Schiff base monomers and dimers revealed that some degree of electronic perturbation has occurred upon dimerization as the Soret bands of the monomers underwent peak broadening along with red shifts. Column chromatography and crystallization were used to purify the compounds. Fourier transform infrared, UV–visible, elemental analysis, ¹H NMR, and mass spectrometry were used to characterize the newly synthesized compounds.     

Kinetics of the reaction of the 2,4,6-tri-tert-butylphenoxyl radical with aromatic amines under quasiequilibrium conditions,and the dissociation energy of the N-H bond in aromatic amines

We have studied the kinetics of the reaction of the 2,4,6-tri-tert-butylphenoxyl radical with 11 aromatic amines under quasiequilibrium conditions. The equilibrium constant for each amine was determined from the kinetic results. These values, together with their temperature dependence, were used to calculate the dissociation energy of the N-H bond in the 11 aromatic amines. By using earlier results for the reaction of the aroxyl radical with cumyl hydroperoxide, catalyzed by aromatic amines, we have calculated the rate constants for the reaction of 10 aminyl radicals with cumyl hydroperoxide and of cumylperoxy radicals with 10 aromatic amines.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 743–749, April, 1990.     

Spectrophotometric determination of aromatic amines by reaction with p-benzoquinone

A comprehensive study is made of the application of the p-benzoquinone spectrophotometric technique to the aromatic amines. The technique involves a reaction with excess p-benzoquinone; the colored products display maximum absorption at 490–510 nm (varying according to the type of the amine used) and E_{1 cm}^1% in the range of 90–380. On the basis of an IR investigation, ethyl alcohol has been selected as a suitable solvent medium for aromatic amine determination. Electron-donating groups react faster and give more intense color than do electron-withdrawing groups. Results with an average recovery of 95% and mean standard deviation of 3.4% are obtained with seven aromatic amines.     

Facile amidation of esters with aromatic amines promoted by lanthanide tris (amide) complexes

The development of catalysts capable of catalyzing amidation of esters with amines to construct amides under mild conditions is of great importance. Compared to aliphatic amines, the direct catalytic amidation of esters with less nucleophilic aromatic amines is rather difficult. Employing simple lanthanide tris (amide) complexes Ln[N (SiMe₃)₂]₃(μ-Cl)Li (THF)₃ as the catalysts, it was found a broad range of aromatic amines and esters were efficiently converted into various amides in good yields under mild conditions. A plausible mechanism for this transformation was experimentally supported as starting from an amide exchange reaction between the lanthanide tris (amide) complex and the substrate amine.     

Heteroacyl azides as acylating agents for aromatic or heteroaromatic amines

The possibility of formation of substituted heterocyclic amides from heteroacyl azides and aromatic or heteroaromatic amines was investigated. Although acylation proceeded in some cases under mild reaction conditions, formation of N,N′-disubstituted ureas was the main process at elevated temperatures.     

A facile procedure for the one-pot synthesis of unsymmetrical 2,5-disubstituted 1,3,4-oxadiazoles

Unsymmetrically 2,5-disubstituted 1,3,4-oxadiazoles were efficiently synthesized from the cyclization-oxidation reaction of acyl hydrazones. Also, the synthesis of the title compounds was achieved by the condensation of acyl hydrazides and aromatic aldehydes in the presence of ceric ammonium nitrate in dichloromethane.     

Analysis of primary aromatic amines using precolumn derivatization by HPLC fluorescence detection and online MS identification

2-(2-phenyl-1H-phenanthro-[9,10-d]imidazole-1-yl)-acetic acid (PPIA) and 2-(9-acridone)-acetic acid (AAA), two novel precolumn fluorescent derivatization reagents, have been developed and compared for analysis of primary aromatic amines by high performance liquid chromatographic fluorescence detection coupled with online mass spectrometric identification. PPIA and AAA react rapidly and smoothly with the aromatic amines on the basis of a condensation reaction using 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) as dehydrating catalyst to form stable derivatives with emission wavelengths at 380 and 440 nm, respectively. Taking six primary aromatic amines (aniline, 2-methylaniline, 2-methoxyaniline, 4-methylaniline, 4-chloroaniline, and 4-bromoaniline) as testing compounds, derivatization conditions such as coupling reagent, basic catalyst, reaction temperature and time, reaction solvent, and fluorescent labeling reagent concentration have also been investigated. With the better PPIA method, chromatographic separation of derivatized aromatic amines exhibited a good baseline resolution on an RP column. At the same time, by online mass spectrometric identification with atmospheric pressure chemical ionization (APCI) source in positive ion mode, the PPIA-labeled derivatives were characterized by easy-to-interpret mass spectra due to the prominent protonated molecular ion m/z [M + H](+) and specific fragment ions (MS/MS) m/z 335 and 295. The linear range is 24.41 fmol-200.0 pmol with correlation coefficients in the range of 0.9996-0.9999, and detection limits of PPIA-labeled aromatic amines are 0.12-0.21 nmol/L (S/N = 3). Method repeatability, precision, and recovery were evaluated and the results were excellent for the efficient HPLC analysis. The most important argument, however, was the high sensitivity and ease-of-handling of the PPIA method. Preliminary experiments with wastewater samples collected from the waterspout of a paper mill and its nearby soil where pollution with aromatic amines may be expected show that the method is highly validated with little interference in the chromatogram.     

Heat-gradient analytical technique for the simultaneous determination of some aromatic amines

A new sensitive analytical technique has been developed for the simultaneous determination of aromatic amines (aniline, p-nitroaniline, m-nitroaniline, o-nitroaniline, 1,3-phenylenediamine, and 1,4-phenylenediamine). It is based on the differential migration of colored derivatives formed by the reaction of diazotized amines with 8-hydroxy quinoline 5-sulphonic acid (FERRON) on a silica gel plate. Quantitative evaluation of amines is made by visual comparison of the intensities of color by spectrophotometry. The Beer’s law, molar absorptivity, and Sandell’s sensitivity have been determined. The effect of the analytical parameters on the migration and analysis have been evaluated. The method is highly reproducible and has been applied to the determination of amines in environmental samples. The text was submitted by the authors in English.     

Carboxymethylalginic acid ethyl ester and its reactions with <Emphasis Type="Italic">N</Emphasis>-nucleophiles

Esters of carboxymethylalginic acid have been prepared; their acylation activity in the reactions with aromatic amines and aromatic carboxylic acids hydrazides have been studied.     

Polymer-supported organotin reagents for regioselective halogenation of aromatic amines

[reaction: see text] Polymer-supported triorganotin halides were used in the halogenation reaction of aromatic amines. Treatment of aromatic amines with n-butyllithium and polymer-supported organotin halides gave the corresponding polymer-bound N-triorganostannylamines, which by treatment with bromine or iodine monochloride gave the para-halogenated aromatic amines with high yields and high selectivities. The polymer-supported organotin halides reagents regenerated during the course of the halogenation reaction can be reused without loss of efficiency. The presence of tin residues in halogenated aromatic amines was also investigated and evaluated at under 20 ppm after three runs.     

Pyrano[4,3-d]pyrimidinium salts 4. Transformations of 5,7-diaryl-1,3-dimethyl-2,4-dioxo-1H,3H-pyrano[4,3-d]pyrimidinium bromides under the action of phenylhydrazines and aromatic acid hydrazides

Reactions of 5,7-diaryl-1,3-dimethyl-2,4-dioxo-1H,3H-pyrano[4,3-d]pyrimidinium bromides with phenylhydrazines and aromatic acid hydrazides have been studied. The reaction of the salts indicated with phenylhydrazine at ∼20 °C results in the pyrylium ring opening, whereas elevated temperature leads to recyclization products, i.e., 1,3-dimethylpyrido[4,3-d]pyrimidine-2,4(1H,3H)-diones. The reactions of the starting bromides with m-carboxyphenylhydrazine and aromatic acid hydrazides lead to 6-(R-amino)-1,3-dimethyl-2,4-dioxo-1H,3H-pyrido[4,3-d]-pyrimidinium salts.     

Alkylation of aromatic amines by tert-enamides: Direct access to protected aminals

Reaction of aromatic amines with tertiary enamides was performed in n-hexane in the presence of acetic acid as an inexpensive and green catalyst at room temperature. This protocol provides the protected aminals through Markovnikov addition reaction with high to excellent yields and regiospecificity. In addition, this procedure was expanded for the synthesis of aminals from commercially available sulfa drugs such as sulfathiazole and sulfabenzamide.     

Benzocyclobutene in polymer synthesis. I. Homopolymerization of bisbenzocyclobutene aromatic imides to form high-temperature resistant thermosetting resins

A series of new bisbenzocyclobutene-terminated aromatic imide monomers has been synthesized from the condensation reaction of 4-aminobenzocyclobutene and the perspective dianhydride in refluxing acetic acid/toluene. The differential scanning calorimetric studies of the foregoing monomers indicated that polymerization exotherms began at 229–250°C and reached their maxima at 258–263°C. The cured samples (250–254°C; N₂; 8 h) were surprisingly stable toward thermo-oxidative degradation; only 7–10% weight loss was observed after 200 h (in air) at 314°C (600°F). At higher temperatures (650 and 700°F), the most rigid structure was the most thermo-oxidatively stable. An approach to enhance both the final glass-transition temperature (T_g cure) and the thermo-oxidative stability of the bisbenzocyclobutene system was to dilute the cure-site density since the cure-site structure is the weakest part of the polymeric structure. Therefore, a series of bisbenzocyclobutene-terminated aromatic imide oligomers were prepared, using various aromatic amines as the chain-extending agents. Meta-phenylenediamine was apparently the most effective in the advancement of both the T_g (cure) and thermo-oxidative stability.