Study of the mechanism of recyclization of furans into thiophenes and selenophenes in conditions of acid catalysis. 6. Experiments with labeled atoms. Quantum chemical calculations of intermediates of recyclization and hydrolysis

The reaction of 2-methyl-5-R-furans (R=Me, Bu, 2,2-pentyl-2-methylpentyl) with H₂ ¹⁸O was investigated. Furans and the corresponding 2,5-alkanediones containing the¹⁸O isotope were obtained. The general characteristics of the recyclization and isotope exchange reactions were established. A kinetic study of recyclization of 2,5-dimethylfuran with¹⁶O and¹⁸O into 2,5-dimethylthiophene was conducted. A reverse kinetic isotope effect was found. The schemes of the mechanisms of these processes were refined based on the experimental data and quantum-chemical calculations of the recyclization and hydrolysis intermediates.See [1] for Communication 5.Scientific-Research Institute of Chemistry, N. G. Chernyshevskii Saratov State University, Saratov 410026. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1035–1042, August, 1997.     

Polyfuryl(aryl)alkanes and their derivatives. 7. New recyclization and cyclization reactions in the 2-hydroxyaryldifurylmethane series

Reaction of 2-hydroxybenzaldehydes with -methylfuran (sylvan) under acid-catalysis conditions was investigated. It is shown that the reaction does not stop at the step involving formation of 2-hydroxyarylfuryl-methanes but proceeds further with opening of one of furan rings and recyclization to 3-furylbenzo-furan derivatives. The latter in turn undergo transformations that lead to new heterocyclic systems — 5,6-dihydro-2,4-dimethyl-4-(5-methyl-2-furyl)-4H-benzo[b]furo[2,3-h]cyclopenta[b]furans. Data from the IR, PMR, and mass spectra, alternative synthesis, and x-ray diffraction analysis were used to confirm structures of the synthesized compounds.For Communication 6 see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 616–626, May, 1993.     

Formation and recyclization of heterocycles

Thiorhodanine is recyclized to 1,2,4-triazole-3-thione by reaction with hydrazine. The intermediate recyclization products were identified. 4-Iminothiazolidone is recyclized to 1,2,4-triazol-3-one by reaction with hydrazine, 1,3-oxazolid-4-one-2-thione forms 2-hydrazonooxazolid-4-one by reaction with hydrazine in neutral solvents. The intermediate transformation products were isolated and indicate that the reaction proceeds as a recyclization of the starting oxazolidone under the influence of hydrazine.See [1] for communication IV.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 39–41, January, 1971.     

Structure and ambiphilic reactivity of indolizines. 6. Scope of the isomerizational recyclization of indolizines

The behavior of substituted 6- and 8-nitroindolizines in the isomerizational recyclization reaction has been examined. A novel method of synthesis of 2-acyl-5- and 7-nitroindoles has been developed, by recyclization of 3-acyl-6- and 8-nitroindolizines. The scope of the isomerizational recyclization of indolizines for the synthesis of indoles has been established.For Communication 5, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 758–764, June, 1990.     

Study of the mechanism of recyclization of furans into thiophenes and selenophenes in conditions of acid catalysis. 4. study of the effect of the solvent and direction of reactions of hydrolysis and recyclization of 2,5-dimethylfuran

The kinetics of hydrolysis of 2,5-dimethylfuran and its recyclization into the corresponding thiophene were investigated in water-alcohol medium W R I and 50% ethyl alcohol in the presence of HCl. It was found that the rates of these reactions are a function of both the initial concentration of the acid component and the concentration of water in the alcohol. The rate of hydrolysis is a function of the dilution of the alcohol to a greater degree than the rate of recyclization.See [1] for Communication 3.Scientific-Research Institute of Chemistry at N. G. Chernyshevskii Saratov State University, Saratov 410026. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 624-628, May, 1995. Original article submitted January 30, 1995.     

Reactions involving the formation and recyclization of heterocycles

The reaction of 5-aryl-1,3,4-oxadiazole-2-thiones with hydrazine and hydrazides proceeds with recyclization of the oxadiazole ring to a triazole ring. Depending on the nature of the aryl residue, adducts of 5-aryl-1,3,4-oxadiazole-2-thiones with hydrazine can be isolated in a number of cases. 6-Aryl-2-methyldihydro-1,2,4,5-tetrazine-3-thiones are formed with methylhydrazine as a result of recyclization.See [1] for communication VIII.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 905–909, July, 1971.     

Transformations of sym-octahydroxanthene-1,8-diones and 1,8-dioxo-sym-octahydroxanthylium salts in recyclization under the influence of amines

The chemical behavior of 9-R-sym-octahydroxanthene-1,8-diones and salts based on them in recyclization reactions under the influence of amines was studied. The effect of the basicity of the amines on the direction of recyclization was established. A method is proposed for the single-stage synthesis of sym-octahydroacridine-1.8-dione oximes based on 1,8-dioxo-sym-octahydroxanthenes. Conditions were worked out for the oxidation of sym-octahydroxanthene-1,8-diones and N-R-decahydroacridinediones to the corresponding salts. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 32–38, January, 2006.     

Synthesis and intramolecular recyclization of 2,2-dialkyl-6-chloro-4-hydroxymethyl-benzo[<Emphasis Type="Italic">f</Emphasis>]isoindolinium salts

The intramolecular cyclization of dialkyl(2-butynyl-4-hydroxy)[3-(p-chlorophenyl)propargyl]ammonium chlorides, catalyzed by aqueous KOH, was realized. It was shown that the obtained products — 2,2-dialkyl-6-chloro-4-hydroxymethylbenzo[f]isoindolinium chlorides — readily undergo recyclization under the action of a twofold molar amount of KOH in aqueous solution with heating with the formation of 4-dialkylaminomethyl-8-chloro-1,3-dihydronaphtho[1,2-c]furans. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 834–840, June, 2007.     

A new intramolecular recyclization in water‐base cleavage reaction of 2,2‐dialkyl‐4‐hydroxymethylbenz[f]iso indolinium bromides and chlorides

The water‐base cleavage reaction of 2,2‐dialkyl‐4‐hydroxymethylbenz[f]isoindolinium bromides and chlorides (2b‐g) and (4a‐g) was investigated. It was established that the above‐mentioned salts in water‐base cleavage reaction undergo intramolecular recyclization. As a result 1,3‐dihydro‐4‐dialkylaminomethyl‐naphto[1,2‐c]furans (5a‐g) are obtained in 62‐72% yields. The same products in 65‐70% yields may be obtained by step cyclization cleavage reaction of dialkyl‐4‐hydroxybutyn‐2‐yl‐(3‐phenylpropargyl) ammonium salts (1b‐g) and (3a‐g) , as well. The structure of the resulting amines 5a‐g are determined and approved by X‐ray diffraction, nmr and ir spectroscopic methods.     

Nitropyridines: III. Synthesis of meta-terphenyls by recyclization of nitropyridinium salts

A two-component Hantzsch synthesis was applied to preparation of nitropyridines and their quaternary salts from various enamines and chalcones based on nitroacetophenone. The recyclization of nitropyridinium quaternary salts under the treatment with an aqueous-alcoholic alkali led to preparation of 5′-methylamino-2′-nitro-m-terphenyl derivatives.     

Steric effects in the recyclization of nitropyridinium salts to nitroanilines

The effect of the degree of branching of alkyl groups attached to the amine nitrogen atom on the recyclization of 1,2,4,6-tetramethyl-3-nitropyridinium iodide to nitroanilines was studied.Decreased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1268–1271, September, 1980.     

Quantum-chemical investigation of the recyclization of 1,2,4,6-tetramethyl-3-nitropyridinium iodide

The recyclization of 1,2,4,6-tetramethyl-3-nitropyridinium iodide was examined within the framework of the CNDO/2 (complete neglect of differential overlap) approximation. The electronic structures of the starting, final, and intermediate structures of two competitive processes were evaluated. The primary formation of one of the products was explained.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1386–1388, October, 1985.     

Study of the mechanism of recyclization of furans into thiophenes and selenophenes in conditions of acid catalysis. 5. Direction of protonation of furans

2,5-Dimethyl-3-D-furan was prepared for the first time. Its recyclization into the corresponding thiophene and selenophene was investigated. The possibility of -C-protonation of the furan ring was confirmed by experimental and quantum chemical data.See [1] for Communication 4.Scientific-Research Institute of Chemistry, N. G. Chernyshevskii Saratov State University, Saratov 410026. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1030–1034, August, 1997.     

Pyrimidine sigma-complexes. 7. The recyclization of 5-nitropyrimidine and its methoxy derivatives upon reaction with the acetylacetone carbanion

A study was carried out on the reaction of 5-nitro and 5-nitromethoxypyrimidines with the acetylacetone carbanion. Benzene and pyridine derivatives are formed as a result of recyclization. The direction of the reaction depends on the position of the substituents in the pyrimidine ring and the nature of the bases.Communication 6, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 508–512, April, 1987.     

Hydrazinolytic recyclization of 2-phenacylbenzothiazole

Hydrazinolytic recyclization of 2-phenacylbenzothiazole proceeds via cleavage of the C—S bond in the ring and is accompanied by oxidation of resulting 2-[(5-phenylpyrazole-3-yl)amino]thiophenol into the corresponding disulfide. The subsequent intramolecular cyclocondensation gives selectively pyrazolo[4,3-b][1,4]benzothiazines.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 735-738, March, 2005.     

Synthesis of 2,7-naphthyridines by the recyclization of trimethylformyl-piperidone

The structure of the product of interaction of the sodium salt of 1, 2, S-trimethyl-3 formylpiperid-4-one with cyanothioacetamide was specified. It was shown that the Knoevenagel adduct formed at the first stage in basic conditions undergoes recyclization with the formation of 1, 2,3,5,6, 7, 8, 8a-octahydro-l-oxo-6, 7, 8a-trimethyl-4-cyano-2, 7-naphthyridine-3-thione, the structure of which was confirmed by the data of physicochemical methods of analysis and chemical conversions.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 512–515, April, 1996.     

Isoquinolone derivatives via a furan recyclization reaction

A new approach to the synthesis of isoquinolone derivatives has been developed. It is based on the protolytic recyclization of amides of 2-carboxybenzylfurans. It was shown that the reaction proceeds via formation of allylic alcohols of isoquinolone series, which under acidic conditions undergo isomerization into the corresponding ketones. A new condensed heterocyclic system of furo[2′,3′:3,4]cyclohepta[1,2-c]isoquinolin-8(6H)-one has been synthesized.     

Cyclization of n-alkylazinium cations with bisnucleophiles. 5. Cyclic adducts and recyclization products in the reactions of benzodiazinium cations with imido esters

The reaction of imido esters that contain an active methylene group with four isomeric benzodiazinium cations, viz., the 1-methylquinoxalinium, 2-methylcinnolinium, 3-methylquinazolinium, and 2-methylphthalazinium cations, was investigated. The 1-methylquinoxalinium cation reacts with imido esters via a scheme involving anionic [3^– +2]-cycloaddition to form tetrahydropyrrolo[2,3-b]quinoxalines. The 2-methylcinnolinium cation forms an adduct with an annelated pyrrole ring. Under the influence of imido esters, the 3-methylquinazolinium cation undergoes recyclization to a 2,3-disubstituted quinoline. The 2-methylphthalazinium cation is inert in this reaction.See [1] for Communication 4.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1549–1553, November, 1981.