Ring transformations of heterocyclic compounds. XVII, 2-(2,4,6-Triarylphenyl) substituted dihydro-1H-imidazolium,dihydrothiazolium and thiazolium salts from 2-methyl derivatives by pyrylium and thiopyrylium ring transformations

The synthesis of hitherto unknown 2-(2,4,6-triarylphenyl) substituted 4,5-dihydro-1H-imidazolium perchlorates 6 , 4,5-dihydrothiazolium perchlorates 8 and thiazolium perchlorates 9 from their 2-methyl derivatives 2 , 4 and 5 , respectively, by a 2,6-[C₅+C] ring transformation of 2,4,6-triarylpyrylium and -thiopyrylium salts 1/10 in ethanol in the presence of an appropriate base ( 6 : sodium ethanolate; 8,9 : anhydrous sodium acetate) is reported. Spectroscopic data of the transformation products and structural influences on their formation via anhydrobases of the salts 2 , 4 and 5 are discussed.     

Ring transformations of heterocyclic compounds. XI. 2,4,6-triarylphenylquinolinium salts from methyl substituted derivatives via (thio)pyrylium ring transformations

The preparation of hitherto unknown 2,4,6-triarylphenyl substituted quinolinium perchlorates 3 from methylquinolinium derivatives 2 by a 2,6-[C₅+C] ring transformation of 2,4,6-triaryl(thio)pyrylium salts 1/4 in the presence of triethylamine/acetic acid is described. Spectroscopic data of the quinolinium perchlorates 3 and their formation via anhydrobases of the salts 2 are discussed.     

Ring transformations of heterocyclic compounds. X. A simple method for the conversion of methyl substituted pyridinium salts into 2,4,6-triarylphenyl derivatives: The first (thio)pyrylium ring transformations with heterocyclic anhydrobases as carbon nucleophiles

The synthesis of 2,4,6-triarylphenylpyridinium perchlorates 3 from methyl substituted derivatives 2 by a 2,6-[C₅+C] ring transformation of 2,4,6-triaryl(thio)pyrylium salts 1/4 in the presence of triethylamine/acetic acid in ethanol is reported. Spectroscopic data of the pyridinium perchlorates 3 and their formation via anhydrobases of the salts 2 are discussed.     

Ring transformations of heterocyclic compounds. XXV. Phenanthrene aldehyde imines via ring transformation of pyrylium salts with methylenedihydroisoquinolines—A novel access to the phenanthrene skeleton

The ring transformation of 2,4,6‐triarylpyrylium salts 1 with 2‐methylenedihydroisoquinolines 6 , generated in situ from the related 2‐methylisoquinolinium salts 2 , in the presence of bases is reported. Whereas the transformation of 1 with 2 ( 6 ) and sodium methoxide in methanol leads to 2‐(2,4,6‐triarylphenyl)isoquinolinium salts, with sodium ethoxide in ethanol the aryl substituted phenanthrene‐9‐carbaldehyde imines 4 are obtained, the structure of which was confirmed by an X‐ray structure determination of the 1‐(4‐methylphenyl) substituted derivative. Acid catalyzed hydrolysis of the imines 4 gives rise to the parent phenanthrene aldehydes. The transformation 1 + 2 ( 6 ) → 4 represents a novel access to the phenanthrene skeleton.     

Ring transformations of heterocyclic compounds. XVI. Spiro[cyclohexadiene-dihydroacridines]. A novel class of spirodihydroacridines by ring transformation of pyrylium salts with 9-methylacridine and its quaternary salts

2,4,6-Triarylpyrylium salts 1 react with the in situ generated anhydrobase of 9,10-dimethylacridinium methosulfate ( 2a ) in the presence of anhydrous sodium acetate in ethanol by a 2,5-[C₄+C₂] pyrylium ring transformation to give the hitherto unknown 6-aroyl-3,5-diaryl-10′-methylspiro[cyclohexa-2,4-diene-1,9′-9′,10′-dihydro-acridines] 3 . When the pyrylium perchlorate 1a is treated under the same conditions with the N-ethyl, N-allyl or N-benzyl substituted acridinium salts 2b-d a dealkylation of these salts occurs and the N-unsubstituted spiro[cyclohexadiene-dihydroacridine] 4a is formed. The same compounds 4 can also be obtained by transformation of the pyrylium salts 1 with 9-methylacridine ( 7 ) and triefhylamine/acetic acid in ethanol. Structure elucidation is performed by an X-ray crystal structure determination of the spiro[cyclohexadiene-dihydroacridine] 3a . Spectroscopic data of the transformation products and their mode of formation are discussed.     

Ring transformations of heterocyclic compounds. XIII. Bis(2,4,6-triarylphenyl) substituted bispyridinium salts from methyl derivatives by double pyrylium and thiopyrylium ring transformations

The synthesis of hitherto unknown 4,4′-bis(2,4,6-triarylphenyl) substituted bispyridinium diperchlorates 3 , in which the N-atoms are linked by a carbon chain, a heteroatom containing a carbon chain or a bis(methylene) substituted aromatic/heteroaromatic ring, from 4,4′-dimethylbispyridinium derivatives 2 by a double 2,6-[C₅+C] ring transformation of 2,4,6-triarylpyrylium and 2,4,6-triarylthiopyrylium salts 1/4 is reported. Spectroscopic data of the bispyridinium diperchlorates 3 and their mode of formation are discussed.     

Ring transformations of heterocyclic compounds. XV. N-(2-hydroxyphenyl) substituted 2-alkylamino-4,6-diarylbenzophenones by ring transformation of 2,4,6-triarylpyrylium salts with anhydrobases of benzoxazolium salts

The synthesis of hitherto unknown N-(2-hydroxyphenyl) substituted 2-alkylamino-4,6-diarylbenzophenones 3 from 2,4,6-triarylpyrylium salts 1 and 3-alkyl-2-methylbenzoxazolium salts 2 in the presence of triethylamine in ethanol by a 2,5-[C₄+C₂] pyrylium ring transformation is reported. Structure elucidation is performed by an X-ray crystal structure determination of the benzophenone 3a. Spectroscopic data of the transformation products and their mode of formation via anhydrobases of the salts 2 are discussed.     

Ring transformations of heterocyclic compounds. XX Benzo‐fused spiro[cyclohexadiene‐dihydroindoles] by ring transformation of pyrylium salts with anhydrobases of benzo[e]‐ and benzo[g]indolium salts

The diastereoselective synthesis of 6‐aroyl‐3,5‐diarylspiro[cyclohexa‐2,4‐diene‐1,2′2′,3′‐dihydro‐1′H‐benzo[e]indoles] 6 and ‐benzo[g]indoles] 7 from 2,4,6‐triarylpyrylium perchlorates 1 and in situ generated 2‐methylene‐2,3‐dihydro‐1H‐benzo[e]indoles 3 or ‐benzo[g]indoles 5 (anhydrobases of the corresponding 2‐methyl‐1H‐benzo[e]indolium perchlorates 2 and 2‐methyl‐3H‐benzo[g]indolium perchlorates 4 , respectively) in the presence of triethylamine/acetic acid in ethanol by a 2,5‐[C₄+C₂] pyrylium ring transformation is reported. Spectroscopic data of the transformation products and their mode of formation are discussed.     

Ring transformations of heterocyclic compounds. XXII. Pyrido[1,2‐a]indolium salts from 2‐methyl‐3H‐indoles by pyrylium mediated three carbon annelation

The synthesis of pyrido[1,2‐a]indolium perchlorates 8,11 from 2,4,6‐triarylpyrylium perchlorates 1 and 2‐methyl‐3H‐indoles 6,9 in the presence of a basic condensing agent (anhydrous sodium acetate, piperidine acetate, triethylamine/acetic acid, triethylamine) in ethanol by a 2,4‐[C₃+C₂N] pyrylium ring transformation is reported. Spectroscopic data of the transformation products and their mode of formation are discussed.     

Ring transformations of heterocyclic compounds. XVIII . Spiro[cyclohexadiene-indolines] with three stereocenters from pyrylium salts and chiral methyleneindolines — an example of a high diastereoselective ring transformation

The diastereoselective synthesis of 6-aroyl-3,5-diarylspiro[cyclohexa-2,4-diene-1,2′-indolines] 4 possessing three stereocenters from 2,4,6-triarylpyrylium perchlorates 1 and chiral methyleneindolines 3 (generated in situ by deprotonation of the corresponding 3H-indolium perchlorates 2 ) in the presence of triethylamine/acetic acid in ethanol by a 2,5-[C₄+C₂] pyrylium ring transformation is reported. Structure elucidation is performed by X-ray structure determinations of the spiro[cyclohexadiene-indolines] 4a, 4p and 4t . The influence of various substituents at C-3 of the methyleneindolines 3 on the stereochemistry of the transformation, mechanistic details as well as spectroscopic data of the products 4 are discussed.     

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.     

Ring transformations of heterocyclic compounds. IX. Trifluoromethyl Substituted 2-Amino-3,4,6-triarylbenzophenones by Ring Transformation of 2,4,6-Triarylpyrylium Salts with Trifluoromethylbenzyl Cyanides

The preparation of hitherto unknown trifluoromethyl substituted 2-amino-3,4,6-triarylbenzophenones 3 by a 2,5-[C₄+C₂] rins transformation of 2,4,6-triarylpyrylium salts 1 with trifluoromethylbenzyl cyanides 2 in the presence of sodium methanolate in methanol is reported. Spectroscopic data of the benzophenones 3 and the mode of their formation are discussed.     

Ring transformations of heterocyclic compounds. XXIII. The UV irradiation product of photochromic 2,4,6‐triaryl‐1‐(spiro[2H‐l‐benzopyran‐2,2′‐indoline]‐6‐yl)pyridinium salts ‐ A phenolate betaine or a pyridinium substituted merocyanine dye?

The synthesis of the novel 2,4,6‐triaryl‐1‐(spiro[2H‐1‐benzopyran‐2,2′‐indoline]‐6‐yl)pyridiniumper‐chlorates 4 by reaction of 5 ‐nitrosalicylaldehydes 6 with 1,3,3‐trimethyl‐2‐methyleneindoline ( 7 ) to 6‐nitro‐spiro[2H‐1‐benzopyran‐2,2′‐indolines] 1 , their stannous chloride reduction to the 6‐amino derivatives 8 , followed by a 2,6‐[C₅+N] ring transformation with 2,4,6‐triarylpyrylium perchlorates 9 , is reported. UV irradiation experiments in twenty solvents of different polarity prove their photochromic properties and show that the photochemically generated negative solvatochromic dyes 5 , formed by ring opening of the benzopyran moiety of 4 , are rather merocyanine than pyridinium phenolate betaine dyes.     

Synthesis and properties of N-hetarylpyridinium salts

Methods for the synthesis of N-hetarylpyridinium perchlorates are examined. The basicity constants of a number of the indicated compounds were measured. It is shown that 2,4,6-trimethyl- and 2,4,6-triphenylpyridinium cations lower the electron density in N-hetarylpyridinium salts. N-Acyl derivatives of 1-(2-benzimidazolylalkyl)-2,4,6-triphenylpyridinium perchlorates were obtained. The corresponding ylids were obtained from 1-(5-tetrazolyl)- and 1-(2-benzimidazolyl)-2,4,6-triphenylpyridinium perchlorates.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 944–949, July, 1978.     

Azulene‐substituted pyranylium salts. Syntheses and products characterization

The synthesis of 4‐azulene‐substituted 2,6‐diphenyl‐ and 2,6‐dimethyl‐pyranylium salts and 2‐azulenesubstituted 4,6‐dimethyl‐pyranylium salts by nucleophilic substitution at pyranylium moiety with various azulenes was studied. The starting materials for 2,6‐diphenyl derivatives were 4 chlorinated pyranylium salts. They were obtained by the halogenation with PCl₅ of corresponding pyranones and were used either in situ or after separation. For the synthesis of dimethyl derivatives the corresponding pyranones were treated with POCl₃ and the resulted intermediate was reacted in situ with azulene. In the aim to study the influence of dihedral angle between azulene and pyranylium planes on the recorded spectra, both moieties were adequately substituted. The obtained results were in accord with the calculated values.     

Synthesis of 3,5-disubstituted 1-amino-1,3,5-triazine-2,4,6-triones (or 1-aminocyanurates) by cyclic transformation of 1,3,4-oxadiazol-2(3H)-one derivatives

The 5-aryl(or methyl)-3-phenylcarbamoyl-1,3,4-oxadiazol-2(3H)-ones 2 , in the presence of sodium hydride in anhydrous dimethylformamide, were transformed into 1-benzamido(or acetamido)-3,5-diphenyl-1,3,5-triazine-2,4,6-trione derivatives 7 in poor yields. However, compounds 7 were obtained in better yields when the sodium salts of 5-aryl(or methyl)-1,3,4-oxadiazol-2(3H)-ones 1 were treated with two equivalents of aryl(or ethyl)isocyanates. Acidic hydrolysis of 1-acetamido-3,5-diphenyl-1,3,5-triazine-2,4,6-trione ( 7i ) provided the corresponding free N-amino derivative 9 . Nitrous deamination of 9 gave the known 3,5-diphenyl-1,3,5-triazine-2,4,6-trione ( 11 ). This cyclic transformation is the first one to be reported providing 1,3,5-triazine-2,4,6-trione derivatives.     

Imination of N-methylpyridinium salts by liquid ammonia-potassium permanganate. A new synthesis of nudiflorine

Reaction of substituted 1-methyl(benzyl)pyridinium salts ( 1 ) with liquid ammonia/potassium permanganate leads to introduction of the imino group at the carbon adjacent to the nitrogen. The regiospecificity of the reaction strongly depends on substituent X: at C-6 for X = H, CONH₂, C₆H₅ and at C-2 for X = CH₃. 3-Aminocarbonyl-1-t-butylpyridinium iodide ( 5 ) on treatment with liquid ammonia/potassium permanganate exclusively gives the 4-imino compound 8 ; ¹H nmr spectroscopy shows that 5 in liquid ammonia gives a mixture of the σ-adducts 4-amino-1,4-dihydro- and 6-amino-1,6-dihydro-3-pyridinecarbonamide ( 6 and 7 ). Surprisingly, an oxodemethylation reaction is observed on treatment of 3-aminocarbonyl-1,6-dimethylpyridinium iodide ( 13 ) with liquid ammonia/potassium permanganate, 1,6-dihydro-1-methyl-6-oxo-3-pyridinecarboxamide ( 14 ) being obtained. This compound can easily be converted by phosphorus oxychloride into the alkaloid nudiflorine ( 15 ).     

13C n.m.r. spectra of some pyrylium salts and related compounds

The ¹³C chemical shifts of several alkyl and phenyl substituted pyrylium perchlorates, together with related pyridine and pyridinium salts, are reported. The shifts in the isoelectronic series benzene, pyridine, pyrylium cation correlate well with charge densities calculated by INDO MO theory. Charge densities also account for the shift changes found at C-3, C-4 and C-5 for protonation of pyridine and 2,4,6-trimethylpyridine. The shift changes observed on protonation for C-2 and C-6, along the series pyridine, 2,4,6-trimethylpyridine and 2,4,6-triphenylpyridine can only be rationalized by consideration of both charge density and π-bond order changes. The effects of alkyl substitution on the shifts of the pyrylium cations are not accounted for by charge density changes. Empirical correlations of these shifts with literature data for the alkylbenzenes and the shifts of the phenyl substituted 6-membered heterocycles are discussed.     

Ring transformations of heterocyclic compounds. XIX. Spiro[dihydropyridine‐indolines] novel heterocycles with two spiro‐condensed N‐containing subunits easy accessible by 1,3‐oxazinium ring transformation

The synthesis of hitherto unknown 1‐benzoyl‐1′,3′,3′‐trimethyl‐4,6‐diphenylspiro[1,2‐dihydropyridine‐2,2′‐indolines] 5 from 2,4,6‐triphenyl‐1,3‐oxazinium tetrafluoroborate ( 1b ) and 1,3,3‐trimethyl‐2‐methyleneindolines 2 (used as such or generated in situ from the corresponding 3H‐indolium salts 4 ) in the presence of triethylamine in anhydrous acetonitrile by a 3,6‐[C₃N+C₂] 1,3‐oxazinium ring transformation is reported. Structure elucidation is performed by an X‐ray structure determination of the spiro[dihydropyridine‐indoline] 5a . Spectroscopic data of the transformation products and their mode of formation are discussed.     

Oxidation and nitrosation of 4-(3-alkylureido)-2, 2, 6, 6-tetramethylpiperidine-1-oxyls to 4-(3-alkyl-3-nitrosoureido)-2, 2, 6, 6-tetramethyl-1-oxopiperidinium salts

4-(3-Alkylureido)-2, 2, 6, 6-tetramethylpiperidine-1-oxyls are rapidly oxidized by N₂O₄ or NOCl to 4-(3-alkylureido)-2, 2, 6, 6-tetramethyl-1-oxopiperidinium nitrates and chlorides, which are then nitrosated to 4-(3-alkyl-3-nitrosoureido)-2, 2, 6, 6-tetramethyl-1-oxopiperidinium salts. The perchlorates of the latter were prepared by an exchange reaction with HClO₄. The nitrosation of alkylureidooxoammonium salts is the first example of chemical modification of oxoammonium derivatives in which the highly reactive >N⁺=O group is inert toward the reagent.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 542–547, March, 1993.