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.     

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.     

Investigation of the mechanism of the recyclization of furans to thiophenes and selenophenes under acid-catalysis conditions. 3. Investigation of the recyclization of homologs and functional derivatives of furan. Quantum-chemical calculations of the objects of the recyclization

The kinetics of the conversion of di-, tri-, and tetraalkylfurans to the corresponding thiophenes were investigated. A correlation between the reactivities and structures of the investigated furans was established. Quantum-chemical calculations of the objects of the recyclization were made. The calculated and experimental data on the reactivities of the investigated compounds were compared. The most likely pathway of the protonation of furans in their recyclization was determined on the basis of calculations of the total energies of the protonated forms.For Communication 2 see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1614–1620, December, 1993.     

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.     

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.     

Synthesis and isomerization recyclization of pyrazino[1,2-α]indoles

A method for synthesis of pyrazinol[1,2-a]indoles with alkyl substituents in position 1 was developed based on indole and isomerization recyclization of their quaternary salts into 9-aminopyrido[1,2-a]indole derivatives was conducted.M. V. Lomonosov Moscow State University, Moscow 119899. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 331–335. March, 1995. Original article submitted February 1, 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.     

New method for synthesis of 2,5-disubstituted thiophenes

The use of hydrogen sulfide at the moment of formation is proposed for the recyclization of furans into thiophenes in acidic media. The advantages of this method are shown.N. G. Chernyshevskii Saratov State University, Saratov 410026, Russia. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 736–738, June, 1999.     

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.     

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.     

Isomerization/recyclization of some 5‐ethoxycarbonyl‐pyrimidines

This communication reports on the investigation of a new recyclization conversion of a pyrimidine ring, which can be referred to as C? C recyclization. In this reaction the nucleophile cleaves the pyrimidine ring at the N(3)‐C(4) bond, and following rotation around the single C(5)‐C(6) bond the new cyclization takes place. This type of recyclization has general applicability, and takes place upon alkali treatment of substituted 4‐methyl‐5‐ethoxycarbonyl‐ and 4‐amino‐5‐ethoxycarbonyl‐pyrimidines (1) which are transformed respectively to 4‐hydroxy‐5‐acetyl‐ and 4‐hydroxy‐5‐carbamoylpyrimidines (2). The obtained pyrimidyl‐ketones can be readily converted to their hydrazones 7‐12.     

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.     

Study of the mechanism of recyclization of furans to thiophenes and selenophenes under theconditions of acid catalysis. 7. The effect of the nature of the nucleophile. The competition constant

Kinetic investigations into the reactions of, 2,5-dimethylfuran with mixtures of hydrogen sulfide and selenide in various quantitative ratios were undertaken, and the competition constant was determined. This made it possible to correlated numerically the nucleophilicity of hydrogen sulfide an selenide in the reaction. For Communication 6, see [1]. I. G. Chernyshevskii Saratov State University, Saratov. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 610–611, May, 1999.     

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.     

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.     

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.     

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.