π-Aromatic complexes of metal carbonyls in the pyrylium salt series

By the reaction of lithium derivatives of cyclopentadienylmagnesiumtricarbonyl, cyclopentadienylrheniumtricarbonyl, and benzenechromiumtricarbonyl with 2,6-disubstituted pyrylium salts the corresponding 4H-pyrans have been synthesized, and the oxidative dehydration of these has given pyrylium cations containing the stated organometallic groups in position 4. It has been shown that the -complexes obtained readily exchange the oxygen of the pyrylium ring for other heteroatoms with the formation of heterocyclic compounds with metallocarbonyl substituents.Translated from Khimiya Geterosiklicheskikh Soedinenii, No. 5, pp. 593–597, May, 1985.     

Synthese von substituierten Pyridiniumsalzen

Derivatives of bis-pyridinium salts—new bifunctional pyridinium perchlorates and monofunctional pyridinium-salts derived from sulfonamides and heterocyclic systems—were synthesized by reaction of pyrylium salts with diamines or monoamino-heterocycles.     

Basicities and transformations of pyrylium and pyridinium salts containing p-aminophenyl substituents

On the basis of the measured basicity constants of pyrylium and pyridinium salts containing p-aminophenyl substituents it is shown that the positive charge in the pyrylium cation is considerably higher than in the pyridinium cation. The constants of the pyrylium and pyridinium substituents, which show that the magnitude of the electronic effect of the pyrylium ring is considerably higher than that of the pyrydinium ring, were calculated. The reaction of the indicated pyrylium salts with some electrophilic and nucleophilic reagents was examined.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1025–1028, August, 1976.     

Ring transformations of heterocyclic compounds. XXI. Diastereoselective built‐up of an aroylcyclohexadiene moiety as second spiro‐connected ring at spiroindolines by pyrylium ring transformation

2,4,6‐Triarylpyrylium perchlorates 1 react with methyleneindolines 3 in situ generated from the corresponding methylindolium salts 2 , which are spiro‐fused with a cycloalkane, benzanellated cycloalkene or a heterocyclic system. These diastereoselective 2,5‐[C₄+C₂] pyrylium ring transformations are carried out in the presence of triethylamine/acetic acid in boiling ethanol to give the dispiroindolines 4 with a trans configuration of the more bulky substituents at the cyclohexadiene ring. By the same type of transformation the dispiro compounds 7/10 with an additional fused benzene ring are obtained from the pyrylium salt 1a and 6/9 , the benzo‐fused analogues of 3 . Spectroscopic data of the transformation products as well as their mode of formation are discussed.     

Introduction of the pyrylium ring into compounds of the aromatic and heterocyclic series

Halogen-substituted pyrylium cations react with organic nucleophilic compounds via an electrophilic mechanism to form new pyrylium salts. The reaction is extended to aromatic, heterocyclic, andnonbenzoid aromatic systems. Pyrylium salts that contain other functional groups do not enter into this reaction. The IR spectra of the compounds obtained are presented.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1320–1323, October, 1971.     

Cyclopropyl-substituted pyrylium salts

The previously unknown 2,4,6-trisubstituted pyrylium salts 1-4 , carrying cyclopropyl and methyl or phenyl substituents in the same molecule, and 5-8 , substituted with isopropyl groups instead of cyclopropyl, were synthesized as perchlorates. The electronic spectra and the C-13 nmr spectra of the two groups of compounds were compared. A cyclopropyl group has a batochromic effect on the electronic spectrum roughly half that exerted by a phenyl; replacement of an alkyl by a cyclopropyl shifts the highest wavelength absorption band by about 20 nm. Presence of phenyl substituents reduces the batochromic effects of cyclopropyl substituents. The effects of both cyclopropyl and phenyl substituents on the electronic spectra are smaller for pyrylium than for tropylium. The nmr signals for all the ring carbons are shifted upfield upon replacement of isopropyl by cyclopropyl; in particular, the effect of substituents in position 2 upon the chemical shift of C(4) indicates that the electron-releasing effect varies in the series alkyl < phenyl < cyclopropyl, in agreement with the findings for 2,6-disubstituted pyrylium salts. The difference between the chemical shifts for the methine and methylene carbons of the three-membered ring is a function of the electron demand of the cationic heterocycle.     

Pyrylium Mediated Transformations of Primary Amino Groups into Other Functional Groups. New Synthetic Methods (41)

The first pyrylium salt was isolated some 80 years ago, yet up to the 1950s only moderate interest was taken in the preparation, properties and uses of such salts. However, the past thirty years has seen a phenomenal growth in the literature pertinent to this area of chemistry: the importance of pyrylium salts as intermediates has been realized. They are readily prepared by a variety of generally applicable routes, and they are highly reactive towards nucleophiles. Together, this enables the convenient synthesis of a great variety of acyclic and heterocyclic compounds. We have used highly substituted pyrylium salts for the two-step conversion of the amino group in alkylamines RNH₂ into numerous other functionalities. In the first step, the pyrylium salts are converted with the amines into N-substituted pyridinium salts, which, in the second step, react with Nu^? to give the desired products RNu. In some cases the R moiety is also changed, e.g. by elimination. Studies of the reactions of these pyridinium salts have allowed interesting insights into the mechanisms of nucleophilic substitution, in addition to rendering aliphatic amines important synthetic intermediates. Thus, the method complements the diazotization procedure for the transformation of arylamines.     

Studies of Some Novel Pyrylium Salts

The preparation is described of some novel pyrylium salts containing ethoxycarbonyl, anthracenyl, and adamantyl substituents.     

利用荧光探针技术研究氧鎓盐光引发丁基乙烯基醚的阳离子聚合

 本工作合成了一组带不同取代基的氧鎓盐化合物,并对它们的荧光寿命、荧光量子产率以及用丁基乙烯基醚(BVE)进行猝灭的荧光猝灭常数进行了测定,发现带拉电子基的氧鎓盐化合物和BVE间存在着较强的相互作用,相反,推电子基的引入则减弱了这种影响,表明反应具有电子转移性质.由于在BVE的聚合过程中,被猝灭的氧鎓盐荧光会因BVE聚合、双键减少而使氧鎓盐荧光逐步恢复.因此利用这一现象作为荧光探针,考察了氧鎓盐光引发BVE的阳离子聚合过程.文中还对氧鎓盐光引发BVE聚合的机理进行了初步讨论.     

利用荧光探针技术研究氧鎓盐光引发丁基乙烯基醚的阳离子聚合

本工作合成了一组带不同取代基的氧鎓盐化合物,并对它们的荧光寿命、荧光量子产率以及用丁基乙烯基醚(BVE)进行猝灭的荧光猝灭常数进行了测定,发现带拉电子基的氧鎓盐化合物和BVE间存在着较强的相互作用,相反,推电子基的引入则减弱了这种影响,表明反应具有电子转移性质.由于在BVE的聚合过程中,被猝灭的氧鎓盐荧光会因BVE聚合、双键减少而使氧鎓盐荧光逐步恢复.因此利用这一现象作为荧光探针,考察了氧鎓盐光引发BVE的阳离子聚合过程.文中还对氧鎓盐光引发BVE聚合的机理进行了初步讨论.     

The pyrylation of aromatic and heterocyclic compounds

Pyrylium salts having no substituents in position 4 react with aromatic and heteroaromatic compounds forming 4-aryl- and 4-heterylpyrylium derivatives. The reaction takes place through the stage of the formation of a pyran which, with an excess of the initial pyrylium salt, splits out a hydride ion, aromatizing into a trisubstituted pyrylium cation.Translated from Khimiya Geterotsiklicheskikh Soedinenii, Vol. 6, No. 6, pp. 733–738, June, 1970.     

Spectra and structure of pyrylium salts

IR spectra of 20 specimens of 5, 6, 7, 8-tetrahydro-2-benzopyrylium 1, 3-disubstituted salts are obtained. The characteristic changes in the valence vibration bands for the pyrylium ring and for aromatic substituents are noted.     

Synthesis of indolizines starting from pyrylium salts

β-N-Pyridinium acetaldehydes with alkyl substituents in the 2 and 6 positions of the pyridinium ring, obtained from the corresponding pyrylium salts, cyclise in alkaline medium to new indolizines. This high-yield reaction sequence is optimal for indolizines unsubstituted in the five-membered ring which are difficultly accessible by other methods.     

Pyrylocyanines. 35. Squarylium dyes based on tert-butyl-substituted pyrylium and thiopyrylium salts

Squarylium dyes based on isomeric di(tert-butyl)methyl-substituted pyrylium, thiopyrylium, and benzopyrylium salts have been synthesized. The dye containing 4, 6-di(tert-butyl)pyrylium residues was converted to its analog with methylpyridinium residues. The PMR and electronic absorption spectra of the dyes obtained were investigated. It was established that deepening of the color from dicarbocyanines to squaraines is characteristic only of dyes containing heterocyclic residues with high or medium electron-donor capacity. For dyes containing heterocyclic residues with low electron-donor capacity the opposite pattern is observed.Institute of Organic Chemistry, National Academy of Sciences of Ukraine, Kiev, 253660. Translated from Khimiya Geterotsklicheskikh Soedinenii, No. 8, pp. 1038–1044, August, 1996. Original article submitted May 8, 1996.For communication 34, see [1].     

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.     

Introduction of new substituents into some aromatic cations

Diverse substituents in the 2- and 6-positions of pyrylium and selenapyrylium salts do not have a substantial effect on the yields in the pyrylation of dimethylaniline and 1-methylindole. The cyclopropenylation and tripylation of these compounds under conditions similar to those in the pyrylation reaction were studied; this study makes it possible to compare these three reactions.     

Thiapyrylium and pyrylium salts with furyl substituents

The possibility of obtaining pyrylium and thipyrylium salts that contain acidophobic furyl substituents by the action of protic acids on the corresponding 1,5-diketones in acetic acid or methanol, depending on the position of the furan rings relative to the carbonyl groups, was established.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1604–1607, December, 1981.     

Pyrylium,pyridine, and N-phenylpyridinium derivatives of cyclopentadienyltricarbonylmanganese

2,4,6-Trisubstituted pyrylium salts containing a cymantrenyl substituent in the 6 position were synthesized by condensation of acetylcymantrene with chalcones. As compared with the corresponding pyrylium derivatives of ferrocene, the pyrylium salts obtained exchange a heteroatom more readily and are more stable. The pyrylium derivatives of cymantrene were converted to the corresponding pyridines by the action of ammonium acetate in glacial acetic acid or an aqueous solution of ammonia and to the corresponding N-phenylpyridinium salts by the action of aniline in acetic acid or alcohol.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 21–24, January, 1979.     

Oxonium Salts in the Synthesis and Spectral Behavior of Pyrano(pyrylium)‐mono methine Cyanine Dyes

Pyrano‐ and pyrylium mono‐8[4(1)] and/or 5(6)‐[2(4)]methine cyanine dyes ( 6a–k , 7a–f ) were synthesized based on acyclic heterocyclic Schiff bases of pyrolo[3,2‐d]pyrazole[oxazole(imidazol‐6‐one)]‐1‐ium iodide salts, 5‐acetyl‐N‐aryl[pyrazolinyl(pyridinyl)]pyrolo‐[5,4‐d]pyrazolin‐iodide salts, and/or (anhydro bases) precursors ( 1a–i , 2a–I , 3a–i , 4a–i , and 5A,Ba–i ). The structure of pyrylium‐9‐chloride and/or iodide and their pyrano(pyrylium)‐mono‐8[4(1)] and 5(6)[2(4)]methine cyanine dyes was identified by elemental and spectral data. The absorption spectra of some selected dyes were investigated in 95% EtOH, polar (nonpolar) organic solvents and in universal buffer solutions to investigate the optimal conditions for the application of such dyes as photosensitizers.     

Sels de pyrylium—XVII: Réactivité des sels de dialcoxy-2,4 pyrylium avec des agents nucléophiles. Formation et propriétés de sels d'amino-2 et de diamino-2,4 pyrylium; sels de dialcoxy-2,4 pyrylium,agents d'alcoylation

Secondary amines react with 2,4-dialcoxy 6-méthyl pyrylium salts to give two new series of 2-amino and 2,4-diamino pyrylium cations. 2,4-Dialkoxy pyrylium salts react as alkylating reagents. A comparison with 1,3-dialcoxy carbonium cations reactivity is reported.