Polymers by the reaction of bis(pyrylium salts) with diamines: A novel approach to ionene polymers

The following reactions of pyrylium salts with amines are described: (1)bis(pyrylium salts) with amines; (2) diamines with pyrylium salts; and (3) bis(pyrylium salts) with diamines. Both (1) and (2) give bis(pyridinium salts) in high yields, and (3) gives the corresponding polymers which are isolated and characterized. This procedure was applied to cationic bis(pyrylium salts) to give cationic dimers and polymers, and further to zwitterionic bis(pyrylium salts) to yield the corresponding zwitterionic dimers and polymers.     

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.     

Reactions of 1,2,4-Oxadiazole[4,5-a]piridinium Salts with Alcohols: the Synthesis of Alkoxybutadienyl 1,2,4-Oxadiazoles

1,2,4-Oxadiazole[4,5-a]piridinium salts add alcohols and alkoxides to undergo electrocyclic ring opening affording alkoxybutadienyl 1,2,4-oxadiazole derivatives. The pyridinium salts represent a special class of Zincke salts that are prone to rearrange to give alkoxybutadienyl 1,2,4-oxadiazoles when treated with suitable nucleophiles or, alternatively, to give pyridones in the presence of bicarbonate. The pivotal tuning of the experimental conditions leads to a straightforward synthesis of valuable 1,2,4-oxadiazole derivatives. The mechanism is also discussed in the light of previous observations.     

Synthesis of pyrimidine derivatives by reaction of pyrylium salts with guanidine and compounds of the guanidine series

2,4,6-Triphenylpyrylium perchlorate reacts with methylguanidine to give 1-methyl-2-amino-4,6-diphenylpyrimidinium perchlorate, which undergoes the Dimroth rearrangement to give 2-methylamino-4,6-diphenylpyrimidine. 2,4,6-Triarylpyrylium perchlorates react with guanidine to give N-pyrimidinylpyridinium salts. Pyrylium salts react with aminoguanidine, sulfanilylguanidine, and symmetrical diphenylguanidine at one amino group to give the corresponding pyridinium salts. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 748–752, June, 1980.     

Recent application of acidic 1,3-azolium salts as promoters in the solution-phase synthesis of nucleosides and nucleotides

Acidic 1,3-azolium salts are prepared from Brønsted acids and 1,3-azoles such as imidazole, thiazole, and oxazole. Acidic imidazolium salts are frequently employed as promoters for the synthesis of nucleotides using the phosphoramidite method in a solution phase. Recently, it was revealed that thiazolium and oxazolium salts catalyzed Vorbrüggen-type N-glycosylation reactions to give nucleosides. These reactivities are attributed to the stronger Brønsted acidities of the thiazolium and oxazolium salts relative to those of the imidazolium salts. This digest focuses on recent progress in the applicability of acidic 1,3-azolium salts as promoters in the solution-phase synthesis of nucleosides and nucleotides.     

Reaction of arylthiacyclanylsulfonium salts with nitrogen bases

When arylthiacyclanylsulfonium salts are heated with nitrogen bases the C-S bond of the heteroring undergoes quantitative cleavage and the base adds to form a C-N bond. These sulfonium salts react with ammonia or pyridine to give ammonioalkyl sulfides; amino sulfides and secondary amine salts are obtained with excess secondary amines. The described reaction is a new preparative method for the synthesis of amino sulfides and ammonioalkyl aryl sulfides.     

Reaktionen der Perthiophosphonsäureanhydride mit Aminen und Ammoniak

Perthiophosphonic anhydrides react with amines to give the corresponding ammonium salts of amido dithiophosphonic acids, while ammonia reacts to give ammonium trithiophosphonates and thiophosphonic diamides. The chemical shifts δ_P of numerous thiophosphonic derivatives are listed.     

Synthesis of mercaptonitroimidazoles and their reaction with 2,4,6-trinitrochlorobenzene

A number of derivatives of mercaptomono- and dinitroimidazoles were synthesized by the action of potassium sulfide on the corresponding halonitroimidazoles. Mono- and dipotassium salts of mercaptonitroimidazoles were obtained. It was established that the monopotassium salts of mercaptomono- and dinitroimidazoles react with 2,4,6-trinitrochlorobenzene to give picrylmercapto derivatives, dipotassium salts of mononitromercaptoimidazoles give, depending on the ratio of the components, picrylmercaptonitroimidazoles or S.N-dipicrylmercaptonitroimidazoles, and dipotassium salts of mercaptodinitroimidazole give only picrylmercaptonitroimidazoles.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 812–816, June, 1982.     

Selective Activation of Fluoroalkenes with N‐Heterocyclic Carbenes: Synthesis of N‐Heterocyclic Fluoroalkenes and Polyfluoroalkenyl Imidazolium Salts

Selective reactions between nucleophilic N,N′‐diaryl‐heterocyclic carbenes (NHCs) and electrophilic fluorinated alkenes afford NHC fluoroalkenes in high yields. These stable compounds undergo efficient and selective fluoride abstraction with Lewis acids to give polyfluoroalkenyl imidazolium salts. These salts react at Cβ with pyrrolidine to give ammonium fluoride‐substituted salts, which give rise to conjugated imidazolium‐enamine salts through loss of HF. Alternatively, reaction with 4‐(dimethylamino)‐pyridine provides a Cα‐pyridinium‐substituted NHC fluoroalkene. These compounds were studied using multinuclear NMR spectroscopy, mass spectrometry, and X‐ray crystallography. Insight into their electronic structure and reactivity was gained through the use of DFT calculations.     

Efficient and Inexpensive Synthesis of Benzimidazoles and Quinoxalines

o-Phenylenediamines were reacted with carbonyl compounds, β-ketoesters, and 1,2-diketones in presence of ammonium salts to give benzimidazoles and quinoxalines in very good yields. Ammonium salts are commercial and environmentally benign catalysts.     

Formylation and vinylformylation of 2,3-cycloalkenobenzopyrylium salts

Heating of 2,3-cycloalkenobenzopyrylium salts in acetic anhydride with excess formylating agent (dimethylformamide, formanilide, N-formylmorpholine, and N-phenyl-N-methyl-aminoacrolein) gives monoiminium salts, the hydrolysis of which yields aldehydes or, in the presence of hydrosulfide, thioaldehydes. On treatment with the Vilsmeier complex, 1-methylquinaldinium salts give diiminium salts, which are hydrolyzed to the corresponding aldehydes.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 733–736, June, 1971.     

Reactions of α-Sulfenyl-N-anions at the Nitrogen Atom. Reactions of N-Substituted Arenesulfenamide Sodium Salts with Isocyanates

N-Arylsulfonylarenesulfenamide sodium salts react with isocyanates in acetone to give N-arylsul- fonyl-N-arylsulfenyl-N'-substituted urea sodium salts which are converted into the corresponding ureas by the action of mineral acids.     

The reaction of 2,4,6-tris(trimethylsiloxy)-1,3,5-triazine with chlorocarbenium ions: a new access to 1-oxa-3-azabutatrienium and 2-azaallenium salts

Chlorocarbenium salts - of the Vilsmeier-Arnold type react with the silylated isocyanuric acid to give 1-oxa-3-azabutatrienium salts under mild conditions. From reactions of diarylchloromethenium salts - with and ketones or tertiary carboxamides high yields of 2-azaallenium salts were obtained. A few chloro substituted 2-azaallenium salts were prepared from and carbonyl compounds. The mechanisms of the new reactions are discussed.     

Addition reaction of zinc acetylides to thioiminium salts leading to 3-amino-1-sulfenyl-1,4-enynes

The reaction of thioiminium salts with zinc acetylides took place at 60 °C to give 3-amino-1-sulfenyl-1,4-enynes in moderate to good yields. Two molecules of acetylides were incorporated into the products. Nucleophilic attack of zinc acetylides to thioiminium salts may initially occur to form alkynyl S,N-acetals, followed by their [1,3]-rearrangement to give 3-sulfenyl-1-aminoallenes.     

Acid-catalyzed acylation of 4-alkyl-3-azapyrylium salts and the synthesis of 4-acylaminopyrylium salts

4-Alkyl-3-azapyrylium salts undergo acylation at the alkyl group under acid-catalyzed conditions to give 4-acylmethyl-3-azapyrylium derivatives, which upon heating in proton-donating solvents recyclize to give 4-acylaminopyrylium salts.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 265–269, February, 1991.     

Thermolysis of 1,2-dithiolylium salts in the ion source of the mass spectrometer

1,2-Dithiolylium salts are thermolysed in the ion source of a mass spectrometer; some salts (group I) undergo thermolysis to give a stable dithiolyl radical where subsequent ionization gives rise to a mass spectrum in which the parent ion corresponds to the dithiolyl ion. The radical may be stabilized before ionization by expulsion of a hydrogen atom to form a neutral dithiole derivative, and then mass spectra exhibit abundant molecular ions corresponding to such dithiole derivatives.Other salts (group II) may expel a proton with formation of a carbene and subsequent dimerization to a tetrathiafulvalene.The thermolytic behaviour of 1,2-dithiolylium salts is compared with their electrochemical behaviour and several analogies are found.     

Pyranylidene iminium salts II. Iminium salts derived from pyrones,dialkylamides and phosphorus oxychloride

N,N-Dialkylamides, pyrones, and phosphorus oxychloride react to give pyranylidene chloroiminium salts. The chlorine atom of these salts is readily displaced by nucleophiles to yield a variety of pyranylidene derivatives.     

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.     

Azonia polycyclic quinones,o-diazo-oxides and related products

4α-Azoniaanthracene-5,6- and 5,8-dione salts have been prepared by nitric acid oxidation of their respective diols, and are shown to function as either an electrophilic dienophile or a diene component in Diels-Alder-type reactions. Several azonia o-quinones have been treated with tosylhydrazine in methanol saturated with hydrogen chloride to give unusually stable o-diazo-oxides. A four-step dehydroxylation procedure is detailed for the conversion of .5,6-dihydroxy-4α-azonia-anthracene salts to new 5-hydroxy-4α-azoniaanthracene salts.     

A versatile synthesis of substituted benzimidazolium salts by an amination/ring closure sequence

[reaction: see text]. A new method to produce benzimidazolium salts based on a successive Buchwald-Hartwig amination and ring closure is reported. A variety of different benzimidazolium salts can be prepared using this procedure. Amines that bear an alpha-chiral group undergo the reaction to furnish chiral benzimidazolium salts. The salts that lack a C2 substituent on the heterocycle are readily deprotonated to give nucleophilic carbenes.