Synthesis of substituted 2- and 4-carboxypyrylium salts

Modified methods for the synthesis of substituted 2- and 4-carboxypyrylium perchlorates and the necessary diphenacylacetic acids are proposed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 162–166, February, 1981.     

2-Benzopyrylium salts. 27. Formation of substituted chrysenes from 1-methyl-2-benzopyrylium salts

1-Methyl-2-benzopyrylium salts with a free position of the heteroring primarily form substituted chrysenes. In alkaline media this process does not proceed through the intermediate formation of 1,5-diketones.For Communication 26, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1472–1476, November, 1984.     

Peptide synthesis with benzisoxazolium salts—I : Properties of substituted 2-ethyl-benzisoxazolium salts

The general features and limitations of 2-ethylbenzisoxazolium fluoroborate as a peptide coupling reagent are described. Strategies for effecting improvements through benzo substitution led to the preparation and study of the 5-nitro, 7-hydroxy, 5-nitro-7-hydroxy, and 4,6-dihydroxy-2-ethylbenzisoxazolium cations. The general properties of these and of several related systems are outlined.     

Some 2-(dialkylamino) substituted chromenylium salts

The reaction of 2-(dialkylamino)-7-methoxychromones with malononitrile in the presence of acetic anhydride afforded [2-(dialkylamino)-7-methoxy-4H-chromen-4-ylidene]malononitriles. When these compounds were refluxed with concentrated hydrochloric (or hydroiodic) acid, 2-(dialkylamino)-7-methoxy(or hydroxy)-4-methylchromenylium salts were obtained. The use of concentrated sulfuric acid or polyphosphoric acid in the hydrolysis was also investigated. The preparation of ethyl [2-(dialkylamino)-7-methoxy-4H-chromen-4-ylidene]cyanoacetates and their behavior when treated with acids are also described, as well as the synthesis of some 3-(dialkylamino)-1-methylnaphtho[2,1-b]pyrylium salts.     

Azulene‐substituted pyridines and pyridinium salts. Synthesis and structure. 2. Azulene‐substituted pyridinium salts

4‐Azulen‐1‐yl substituted 2,6‐dimethyl‐and 2,6‐diphenyl‐pyridinium salts are obtained in yields between 50 % and 100 % in the reaction of corresponding 4‐azulen‐1‐yl‐pyranylim salts and various amines. The effects of amine structure and of substitution in the heterocycle or at azulene moieties on the synthesis have been investigated. The uv‐vis and NMR spectra of reaction products are examined and discussed in correlation with their structure.     

Recyclization of diethoxymethyl substituted benzimidazo-fused thiazolium salts

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Photochemical reactions of substituted cyclopropenium salts.

Photochemical reactions of triphenylcyclopropenium tetrakis(pentafluorophenyl)gallate (TPCPGa) and diphenyl-(2-methoxy-1-naphthyl)-cyclopropenium tetrakis(pentafluorophenyl)gallate (DPMNCPGa) (Chart 1) have been investigated in acetonitrile. Traces of water were required for the photochemical reactions to proceed. The disappearance of both TPCPGa and DPMNCPGa obeys zero-order kinetics with rate constants (k) having a linear dependence on the concentration of water. Electron-transfer from water to the cyclopropenium cation is proposed as the primary process in the formation of the cyclopropenyl radical. The latter dimerizes leading to the photoproducts.     

Oxidation of propane over substituted Keggin phosphomolybdate salts

Ammonium salts, (NH₄)₆HPMo₁₁MO₄₀ (M = Ni, Co, Fe), have been investigated for the oxidation of propane, with molecular oxygen, at temperature ranging between 380 °C and 420 °Cafter in-situ pre-treatment performed at two heating rate of 5 or 9 °C/min. They were characterized by BET method, XRD, ³¹P NMR, UV-Vis and IR techniques. The catalysts were found active in the propane oxidation and selective to propene or acrolein, in particular for samples pre-treated with the heating rate of 9 °C/min.     

The ammonia-free partial reduction of substituted pyridinium salts

This paper reports a study into the partial reduction of N-alkylpyridinium salts together with subsequent elaboration of the intermediates thus produced. Activation of a pyridinium salt by placing an ester group at C-2, allows the addition of two electrons to give a synthetically versatile enolate intermediate which can be trapped with a variety of electrophiles. Furthermore, the presence of a 4-methoxy substituent on the pyridine nucleus enhances the stability of the enolate reaction products, and hydrolysis in situ gives stable dihydropyridone derivatives in good yields. These versatile compounds are prepared in just three steps from picolinic acid and can be derivatised at any position on the ring, including nitrogen when a p-methoxybenzyl group is used as the N-activating group on the pyridinium salt. This publication describes our exploration of the optimum reducing conditions, the most appropriate N-alkyl protecting group, as well as the best position on the ring for the methoxy group. Electrochemical techniques which mimic the synthetic reducing conditions are utilised and they give clear support for our proposed mechanism of reduction in which there is a stepwise addition of two electrons to the heterocycle, mediated by di-tert-butylbiphenyl (DBB). Moreover, there is a correlation between the viability of reduction of a given heterocycle under synthetic conditions and its electrochemical response; this offers the potential for use of electrochemistry in predicting the outcome of such reactions.     

Synthesis of oxazolyl‐substituted morpholinium salts

Morpholinium salts coupled to oxazolyl moieties have been synthesized via nucleophilic substitution of a series of oxazolyl chlorides with morpholine. The oxazole moieties were first synthesized and then coupled with morpholine. The corresponding hydrochloride and methyl iodide salts were obtained, purified, characterized and then tested for muscarinic receptor binding affinity. Biological test results from MDS Pharma Services revealed no significant muscarinic receptor affinity.     

Reactions of substituted phenazine salts with nucleophilic reagents

The condensation of 1-chloro-, 1-phenyl-, 3-chloro-, 3-cyano-, and 3,7-dimethoxy-substituted phenazinium salts with malonic and cyanoacetic esters, N-methylrhodanine, 2-methylbenzothiazolium and quinaldinium salts, aniline, and morpholine was studied. The absorption spectra of the synthesized dyes are described.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1425–1429, October, 1972.     

Reduction of substituted 1H-4,5-dihydroimidazolium salts

Reactions of several substituted 1H-4,5-dihydroimidazolium salts 1 with nucleophilic and electrophilic reducing agents acting via hydride transfer were explored. Reaction of compounds 1 with lithium aluminum hydride in THF afforded the corresponding imidazolidines 2 . When alkaline borohydrides (sodium borohydride, potassium borohydride, sodium cyanoborohydride) in ethanol at room temperature were used, partial or total over-reduction of compounds 2 leading to N,N,N'-trisubstituted ethylenediamines took place on occasion. Results may be explained taking into account that reductive cleavage of 2 proceeds via a stabilized iminium ion present in protic solvents. Treatment of compounds 1 with an excess of borane in THF afforded the corresponding imidazolidines 2 or their borane complexes, according to the substituent type.     

Regioselective synthesis of new functionally substituted tetrazolium salts

The 1,4-, 1,3-di- and 1,3,5-trisubstituted tetrazolium salts were obtained regioselectively and with high yields by the quaternization of 1- and 2-monosubstituted and 1,5-disubstituted tetrazoles with diacetone alcohol in perchloric acid. An X-ray crystallographic analysis of 1-(2-methylpentan-4-on-2-yl)-4-methyltetrazolium perchlorate was undertaken.Scientific-Research Institute of Physicochemical Problems, Belorus State University, Minsk; e-mail: fhp@fhp.bsu.unibel.by. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1222–1229, September, 1999.     

Structure of nitramine salts

Conclusions The previously proposed structure for the salts of primary nitramines was corro-borated on the basis of the vibrational spectra and quantum-chemical calculations.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 948–950, April, 1972.The authors wish to thank S. Gagarin, who took part in the calculations.     

Structure of the alkaline salts of 2-phenyl- and 2-p-methoxyphenylimino-4-thiazolidinones

The structure of the undissociated molecule of the alkali salt of 2-arylimino-4-thiazolidinone conforms with the more stable tautomer of the NH acid: the iminotautomer. In the free anion formed by the dissociation of the salt the negative charge is concentrated mainly at the ring nitrogen atom; however, a negligible resonance delocalization of the charge to the exocyclic oxygen and nitrogen atoms takes place. Such a charge distribution of the anion is also retained in the crystalline state, thanks to the fact that the lattice structure allows the coordination of the cation with the heteroatoms of the mesomeric fragment of the anion.Translated from Khimiya Getertsiklicheskikh Soedinenii, No. 10, pp. 1399–1404, October, 1986.