Electrochemical reduction of N-(2-nitro-4-R-phenyl)pyridinium salts using redox-mediators

Electrochemical reduction of N-(2-nitroaryl)pyridinium chlorides was accomplished in acidic aqueous alcoholic medium in the galvanostatic mode using tin, titanium, vanadium, and iron chlorides as redox-mediators. The use of SnCl₂ as a mediator catalyst made it possible to shorten the electrosynthesis time as compared to the direct electroreduction on an electrode and prepare the intramolecular cyclization products, viz., substituted pyrido[1,2-a]benzimidazoles, in high yield. The influence of the mediator nature and its amount, current density, temperature, cathode material, medium acidity, and the substrate structure on the efficiency of reductive heterocyclization of N-(2-nitroaryl)pyridinium salts was studied.     

Pd-Cu-catalyzed synthesis of N-(2E,4)- and N-(2Z,4)-enyne cyclic amines

By Pd-Cu-catalyzed coupling of (2E)- and (2Z)-3-chloroprop-2-en-1-ylamines and alkynes a stereoselective method of the synthesis was developed for a series of (2E,4)- and (2Z,4)-enyne cyclic amines.     

Reactions of 6-benzyl-5-methyl-2-(methylsulfanyl)pyrimidin-4(3H)-one with aliphatic and aliphatic-aromatic amines

Russian Journal of Organic Chemistry - The rules were investigated of the regioselective synthesis of N2-substituted derivatives of 2-amino-6-benzyl-5-methylpyrimidin-4(3H)-one from...     

Recyclization of 2-(2-acylethyl)pyridinium salts

Recyclization of 2-(2-acylethyl)pyridinium salts on treatment with nucleophiles may occur in different ways, to give heterocyclic compounds of various classes, namely indoles (the Kost-Sagitullin reaction products), 4-aminoindoles, and 3-hydroxy-1,2,3,4-tetrahydroquinolines, the formation of which constitute novel reactions in the recyclization of pyridinium salts.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1217–1225, September, 1990.     

Reactions of 4-methoxypyrylium salts with secondary amines

4-Aminopyrylium derivatives were prepared from secondary amines and 4-methoxy-2,6-dimethylpyrylium perchlorate ( 1a ) and the corresponding 2,6-diphenyl derivative. Excess amine or elevated temperature resulted in the addition of two equivalents of amine to 1a . The reactions of the aminopyrylium salts with hydroxide, ammonia, primary amines, hydrazines, cyanoacetamides, ethyl cyanoacetate, malononitrile, nitromethane, sodium sulfide, and a Grignard reagent are described.     

Intramolecular photocyclization of N-[(2-haloaryl)methyl]pyridinium and n-(arylmethyl)-2-halopyridinium salts

Various N-[(2-haloaryl)methyl]pyridinium, N-(arylmethyl)-2-halopyridinium and N-(2-halobenzyl)iso-quinolinium salts have been synthesized and their intramolecular photocyclization reactions studied. Upon irradiation the aqueous solution of N-[(2-haloaryl)methyl]pyridinium, and N-arylmethyl-2-halopyridinium salts 1, 2 were cyclized to give isoindolium salts. In contrast to the pyridinium salts 1, 2 , the aqueous solution of N-(2-halobenzyl)isoquinolinium salts 3 appear not to undergo photocyclization. N-Benzyl-2-chloropyridinium salts 1c is more reactive than N-(2-chlorobenzyl)pyridinium salt 1a in the photocyclization. N-(2-Chlorobenzyl)-2-chloropyridinium salt 1d is three times more reactive than 1c . A mechanism of π-complex formation of the halogen moiety of the pyridinium ring with the phenyl ring is suggested for the reactive pyridinium salt. The triplet energy of the isoquinolinium salts 3 is tool low to photocyclize.     

Reactions of isoquinoline derivatives with pyridinium salts yielding 4-naphthylpyridines

Regiospecific introduction of the 2-naphthyl residue into position 4 of the pyridine ring occurs in the reactions of isoquinolinium salts with 4-methylpyridinium salts through the intermolecular transformation of the isoquinoline bicyclic system involving the methyl group of the pyridinium salt. The reaction occurs under the action of methylammonium sulfite in an aqueous medium on heating. This method provides ring transformation not only for isoquinolinium salts but even for unsubstituted isoquinoline.     

Reactions of 4-ethoxyflavylium, 4-ethoxychromylium,and 4-ethoxyfurochromylium salts with several amines

The reactions of 4-ethoxyflavylium, 4-ethoxychromylium, and 4-ethoxyfurochromylium salts in acidic media with several acids were investigated. In the reaction with hydrazine the furochromylium salt forms pyrazole, whereas both α,β-substituted benzopyrylium salts are converted to azines. The reaction of hydroxylamine with the flavylium salt gives a flavone oxime, whereas the reaction with the furochromylium salt gives an isoxazolylbenzofuranol.     

Birefringence dispersion of N-(4-methoxybenzylidene)-4-butylaniline (MBBA) determined from channeled spectra

The birefringence of MBBA, determined from the channeled spectra, decreases when the wavelength increases, showing a normal dispersion. The changes induced by an external electrostatic field acting perpendicular on the nematic director in the birefringence values were evidenced. The birefringence increases with the electrostatic field intensity which enhances the preferential alignment by the big values of the electric dipole moments induced parallel to the long MBBA molecule. The main refractive indices were interferometrically measured for three visible monochromatic radiations and the birefringence values were concordant with those estimated from the channeled spectra. The main molecular polarizabilities were estimated.     

Reactions of 2-(4-hydroxyanilino)-1,4-naphthoquinones with cerium ammonium nitrate and pyridinium chlorochromate

Reactions of 2-(4-hydroxyarylamino)-1,4-naphthoquinones with cerium ammonium nitrate or pyridinium chlorochromate depending on the structure of initial substrate and the type of reagent led to the formation of 2-chloro-3-(4-cyclohexa-2,5-dienylideneamino)-1,4-dihydronaphthalene-1,4-diones, 2-(4-hydroxy-3-nitrophenylamino)-1,4-naphthaquinones, and also to simultaneous oxidation and chlorination.     

Reaction of hexafluoro-N-(4-N,N-dialkylaminophenyl)-1,4-naphthoquinon-4-imines with primary amines

Amination of 2,3,5,6,7,8-hexafluoro-N-(4-N,N-dialkylaminophenyl)-1,4-naphthoquinon-4-imines with primary amines led to the formation of 3-amino derivatives, which further underwent cyclization into 7-alkyl(aryl)-1,2,3,4,6-pentafluoro-5H-benzo[a]phenazin-5-ones. The spectral properties of compounds obtained were examined.     

Reaction of 2-chloro-3-(4-N,N-dimethylaminoanilino)-1,4-naphthoquinone with cyclic amines (piperidine,morpholine, and pyrrolidine)

It was shown that the reaction of 2-chloro-3-(4-N,N-dimethylaminoanilino)-1,4-naphthoquinone with piperidine in the absence of a solvent gives not only a product of replacement of the chlorine atom by a piperidino group, 3-(4-N,N-dimethylaminoanilino)-2-piperidino-1,4-naphthoquinone, but also 2-(4-N,N-dimethylaminoanilino)-1,4-naphthoquinone and 2-(4-N,N-dimethylaminoanilino-2-piperidino)-1,4-naphthoquinone. The latter compounds are the only reaction products formed in dimethyl sulfoxide. The reaction with morpholine occurs in a similar way, whereas that with pyrrolidine gives only a product of replacement of the chlorine atom by hydrogen.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2451–2454, December, 1995.     

2-甲基-3-(4-对甲氧基苯基)-5-(3-甲氧基苯基)异噁唑啉及其生物活性

采用1,3-偶极环加成反应合成了2-甲基-3-对甲氧基苯基-5-间甲氧基苯基异噁唑啉,分离了顺、反异构体,采用核磁共振氢谱分析表征了顺反异构体的谱图行为,对异构体的生物活性进行了测定,新杀菌剂2-甲基-3-对甲氧基苯基-5-间甲氧基苯基异噁唑啉对病菌的有效成分为反式结构,顺式体为无效成分.     

Thermal analysis of salts from 4-nitrophenol and aliphatic amines

In this work, the thermodynamic performance of a single slope solar still with cotton cloth energy storage medium was compared with a simple solar still without energy storage. Two solar stills with similar dimensions (one with cotton cloth energy storage and another without energy storage) were fabricated and investigated its performance under the hot humid climatic conditions of Chennai in India during the summer months of 2017. The performance was evaluated in terms of energy and exergy analysis based on first and second law of thermodynamics, respectively, for 2 mm, 4 mm, 6 mm and 8 mm cotton cloth thickness. The results showed that the maximum energy and exergy efficiency of a solar still was observed to be 23.8% and 2.6%, respectively, for 6 mm cotton cloth thickness. The results confirmed that the cotton cloth regenerative medium has enhanced the still productivity by about 24.1% when compared to the solar still without heat storage.