Ambidentate reactivity of 3-azapyrylium systems in nucleophilic attack reactions

It has been shown that recyclization of 4-acylmethyl-3-azapyrylium salts under the influence of primary amines affords 4-(-hydrozystyryl)pyrimidinium salts, which, upon further heating with the amine, are recyclized to form 4-acylaminopyridinium salts. It has been established that nucleophilic attack of 6-acylmethyl-substituted 3-azapyrylium salts in aqueous NaOH solution leads to functionally substituted pyridines. By means of MNDO quantum-chemical calculations with an accounting for solvation effects, in a continuum model, it has been shown that two directions of nucleophilic attack of the azapyrylium ring — at positions 2 and 6 — are equally probable.Rostov State University. Scientific-Research Institute of Physical and Organic Chemistry, Rostov State University, Rostov-on-Don 344010. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 697–700, May, 1994. Original article submitted April 18, 1994.     

Condensation of 6-methyl-3-azapyrylium salts to pyrido[1,2-c]pyrimidinium derivatives

Under the influence of DMF/Ac₂O 2,4-diphenyl-6-methyl-3-azapyrylium perchlorates undergo condensation to give pyrido[1,2-c]pyrimidinium perchlorates. The structure of one of the perchlorates was proved by x-ray diffraction analysis.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1556–1561, November, 1991.     

Reactions of 2- and 4-methylpyrylium salts with ethyl orthoformate

Under mild conditions 2- and 4-methylpyrylium salts react with ethyl orthoformate to give their β-ethoxyvinyl derivatives. Symmetrical and unsymmetrical cyanine dyes were synthesized by heating the latter with 2- and 4-methylpyrylium salts or N-methylquinaldinium perchlorate. The pyrylocyanines react with perchloric acid to give bispyrylium salts, and they are converted to the corresponding pyridine bases by the action of ammonium acetate.     

Some reactions of 4H-pyrylium salts with tributylphosphine and with tertiary amines

The phosphonium salt from tributylphosphine and 2,6-di(4-methoxyphenyl)pyrylium perchlorate (3) reacted with diisopropylethylamine in acetonitrile to give 2,2′,6,6′-tetra(4-methoxyphenyl)-Δ^4.4′-bi-4H-pyran in quantitative yield. The reaction of 3 and other 4H-pyrylium salts with tertiary amines gave 4H-pyrans.     

Synthesis of 4H-1,3-benzoxazin-4-onium salts and 4-H-1,3-benzoxazin-4-ones

Salicylamide and its substituted derivatives react with aliphatic carboxylic acid anhydrides and perchloric acid to give 4H-1,3-benzoxazin-4-onium salts. These same compounds were obtained by acidic cyclization of O- and N-acylsalicylamides. The synthesized salts are converted to 2-substituted 4H-1,3-benzoxazin-4-ones by the action of triethylamine and are hydrolyzed by water to N-acylsalicylamides. The probable reaction scheme is examined.     

Reaction of indolylpyrylium salts with some hydrazine derivatives

The reaction of 4-(3-indolyl)pyrylium salts with phenylhydrazine in alcohol gives 5-(3-indolyl)pyrazoles. The pyrylium salts react with acid hydrazides in refluxing dimethylformamide to give monohydrazones of the pseudobases of these salts (unsaturated 1,5-diketones).Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 184–186, February, 1972.     

Synthesis of dialkyl 4-methylnaphth[f]isoindolinium salts

Dialkyl(3-chloro-2-butenyl)(3--naphthylpropargyl)ammonium chlorides undergo dehydrochlorination-cyclization in basic medium to give condensed isoindolinium salts.Communication 212 in the series Investigations of amines and ammonium salts; for Communication 211 see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 495–498, April, 1992.     

Reactions of 4-halo-2-alken(arylen)ylphosphonium salts with binucleophiles

Phosphonium salts with a 4-bromo-3-chlorobut-2-enyl or a 3-chlorobuta-1,3-dienyl group react with phenylhydrazine to give phenylhydrazones of corresponding 4-phospohonio-substituted 2-chloro-2-butenals. Reactions of phosphonium salts containing a 4-bromo-3-chlorobut-2-enyl group with a series of binucleophiles were studied. Under the action of urea, 1,4-dehydrobromination takes place to form a salt with a conjugated diene group, which undergoes partial 3,4-3,4-cyclization under the reaction conditions. Nucleophilic substitution reactions of [o-(bromomethyl)benzyl]triphenylphosphonium bromide with binucleophiles were also carried out.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 12, 2004, pp. 1992–1997.Original Russian Text Copyright © 2004 by Ovakimyan, Barsegyan, Pogosyan, Kikoyan, Panosyan, Indzhikyan.This revised version was published online in April 2005 with a corrected cover date.     

Polarographic reduction of benzazolylsubstituted pyridinium salts

N-Methyl- and N-benzyl-substituted 2-, 3-, and 4-benzazolypyridinium (BAP) salts are reduced on a dropping mercury electrode (DME) to give a free radical in the first step and the corresponding dihydropyridine derivative in the second step. The free radicals of 2- and 4-BAP salts are distinguished by high stability as compared with other radicals with a pyridine structure owing to delocalization of the unpaired electron over the conjugated system and can be recorded by ESR spectroscopy. A peculiarity of the BAP salts is their facile reduction on the electrode; this is particularly true of the 2- and 4-benzoxazolyl- and benzothiazolyl-substituted salts.     

Synthesis of a family of 3-alkyl- or 3-aryl-substituted 1,2-dihydroquinazolinium salts and their isomerization to 4-iminium-1,2,3,4-tetrahydroquinolines

A straightforward synthesis of substituted 1,2-dihydroquinazolinium triflates (3) is reported by reaction of 2-imino-substituted anilines with a range of carbonyl compounds in the presence of triflic acid via intermediate iminium salts. Similar reactions with di- or trialdehydes and triflic acid give bis- or tris-(1,2-dihydroquinazolinium) salts. Some 4-methyl substituted 1,2-dihydroquinazolinium salts rearrange, under various conditions, to their corresponding 4-iminium-1,2,3,4-tetrahydroquinolinium isomers (7). Most of salts 3 derived from ketones are rather unstable, which prevents their isolation or full characterization. The crystal structures of various 3 and 7 salts have been determined.     

Direction of deprotonation of 4-(3-indolyl)pyridinium salts in alkaline media

A proton is split out from the NH group of indole to give the anhydro bases in all cases when 4-(3-indolyl)pyridinium salts with alkyl, benzyl, phenacyl, and quinolylmethyl residues attached to the pyridinium nitrogen atom are treated with alkali.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1645–1647, December, 1981.     

The preparation of 4-substituted pyrylium salts and their use in dienal synthesis

The unsubstituted pyrylium nucleus is shown to undergo reaction with cuprate or secondary Grignard organometallic reagents to give intermediate 4-substituted pyrans which are converted into the corresponding 4-substituted pyrylium salts (7 examples) in fair to good overall yield. The synthetic utility of the 4-substituted pyrylium heterocycles is demonstrated by their reaction with organolithium reagents to give 3,5-disubstituted dienals in a highly stereospecific manner (7 examples) via electrocyclic ring opening of the intermediate 2-substituted pyrans.     

Syntheses and photophysical properties of some 4‐arylpyridinium salts

A number of 4‐arylpyridines, many methoxy substituted, were prepared by an efficient two‐step method involving aryl Grignard addition to 1‐methyl‐4‐piperidone and direct aromatization of the resulting 4‐aryl‐4‐piperidinols. The pyridines were N‐alkylated to give sulfonate salts desired for their fluorescent properties. Study of selected compounds as laser dyes revealed several structures to be efficient dyes lasing in the 530‐550 nm range. Two new diazaquaterphenyls were prepared and were quaternized. These salts exhibited intense fluorescence in the 420‐450 nm range, but would not lase. A phenolic azaterphenyl suitably substituted for excited state intramolecular proton transfer (ESIPT) did not fluoresce at all.     

Substituted 4(5H)-oxazolones and their salts. 3. Synthesis of 4(5H)-oxazolonium salts from amides of 2,4-dihydroxy-3,3-dimethylbutanoic acid

2-Alkyl-substituted 4(5H)-oxazolonium salts were synthesized by the reaction of amides of 2,4-dihydroxy-3,3-dimethylbutanoic (pantoic) acid with aliphatic carboxylic acid anhydrides in the presence of an equimolar amount of perchloric acid. The hydrolysis of these salts was realized. Various acyl derivatives of pantoic acid amides were obtained, and the possibility of their cyclization to give 4(5H)-oxazolonium salts under the influence of condensing reagents was demonstrated. The mechanism of the heterocyclization of pantoic acid amides is discussed on the basis of these results.See [1] for communication 2.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 894–900, July, 1981.     

Recyclization reactions of heterocyles. XVII. Hydrazination of 1, 3, 4-oxadiazolium salts

2, 5-Diaryl-3-alkyl-1, 3, 4-oxadiazolium salts react with hydrazine to give acyclic hydrazinolysis products or products of recyclization with participation of the carbon atom in the 2 position of the oxadiazole ring, i.e., dihydro-sym-tetrazines and N-amino-sym-triazoles (with hydrazine) and 2-phenyl-5-aryl-1, 3, 4-oxadiazoles (with benzoylhydrazine) or formazans (with phenylhydrazine).See [1] for communication XVI.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 629–634, May, 1976.     

Synthesis and recyclization of 4-chloromethylflavylium and 4-chloromethylbenzothiapyrilium salts

Condensation of -chloro-o-hydroxyacetophenones in the presence of perchloric acid yields 4-chloromethylflavylium perchlorates. 4-Chloromethylbenzothiapyrilium perchlorates were obtained by intramolecular cyclization of 2-arylmercapto-5-chloropentanones-4. In the reaction of 4-chloromethylflavylium salts with aqueous alkali, chloromethyleneflavenes (the anhydro bases of the starting salts) and 3-phenacylbenzo[b]furanes were separated.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 766–769, June, 1987.     

Reaction of some pyrylium salts with hydrazine

2,6-Diphenyl- and 2,6-di-tert-butylpyrylium salts react with excess hydrazine to give 1,2-diazeplne derivatives. Under the same conditions, 4-(1-methyl-3-indolyl)flavylium perchlorate forms 3-phenyl-5-(1-methyl-3-lndolyl)pyrazole.Translated from Khimiya Geterotsiklichesikikh Soedinenii, No. 1, pp. 45–48, January, 1973.     

Reaction of 4-ethoxychromylium salts with some amines

The reactions of 4-ethoxychromylium salts with some amines were studied. It was shown that o-hydroxyarylpyrazoles and chromone phenylhydrazones, respectively, are formed by the reaction of these salts with hydrazine and phenylhydrazine. The action of primary aromatic amines leads to replacement of the 4-ethoxy group by a 4-arylamino group, while the reaction of the 4-ethoxychromylium salts with N,N-diethylaniline gives 4-ethoxy-4-diethylaminoflavylium salts.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1112–1114, August, 1971.     

Fluorination of 4-nitroisoxazoline salts. Synthesis of 4-fluoro-4-nitroisoxazolines and 4-fluoroisoxazoles

Methods for the synthesis of hitherto unknown 4-fluoro-4-nitroisoxazolines by fluorination of 4-nitroisoxazoline salts with FClO₃ in MeOH and 4-fluoroisoxazoles by treatment of fluoronitroisoxazolines bearing the hydrogen atom bound to the C(5) atom of the isoxazole ring with MeONa in MeOH were developed.     

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.