Ambident Properties of 4-Substituted Thiosemicarbazides in Condensations with Fluoroacetic Acids

4-Substituted thiosemicarbazides react with di- and trifluoroacetic acids to give the corresponding 3-fluoroalkyl-4,5-dihydro-1,2,4-triazole-5(1H)-thiones. Condensation of 4,4-disubstituted thiosemicarbazides with trifluoroacetic acid leads to formation of 2-amino-5-trifluoromethyl-1,3,4-thiadiazoles.     

A study of the behaviour of 2,4-substituted thiosemicarbazides toward orthoesters: Formation of mesoionic compounds

The reactions beetwen 2,4-disubstituted thiosemicarbazides and orthoesters in refluxing xylene led to the formation of the 1,2,4-triazoline-5-thione ring and to the 1,2,4-triazolium-5-thiolate ring. The formation of the mesoionic componds is due to rearrangement of the easily available 2,4-disubstituted thiosemicarbazides to 1,4-disubstituted thiosemicarbazides under the reaction conditions adopted. This method can be usefully used for the synthesis of mesoionic compounds, especially in the case of the 2-methyl-4-phenylthiosemicarbazide.     

The reactions of thiosemicarbazides and 5-halovalerophenones

5-Halovalerophenones reacted with substituted thiosemicarbazides affording two different heterocyclic ring systems. Reactions with 4-substituted thiosemicarbazides gave 3-aryl-4,5,6,7-tetrahydro-1H-1,2-diazepine-1-carbothioamides whereas reactions with 2,4-dimethylthiosemicarbazide gave hexahydro-1,3-dimethyl-8a-aryl[1,2,4]triazolo[1,5-a]pyridine-2(3H)-thiones.     

Synthesis of 4-(pyrazol-5-yl)-1,2,4-triazole-3-thiones

Condensation of pyrazolyl isothiocyanates 2 with N-substituted hydrazines provided the 2-methyl/phenyl-4-(pyrazol-5-yl)thiosemicarbazides 3 . Cyclization of 3 with formic acid-acetic anhydride or with triethyl orthoacetate-acetic anhydride provided 4-(pyrazol-5-yl)-l,2,4-triazole-3-thiones 4a-f and 5-methyl-4-(pyrazol-5-yl)-1,2,4-triazole-3-thiones 4g-I respectively.     

Synthesis of new 1,2,4-triazolines and 1,3,4-thiadiazolines from bithioureas

2,4-Disubstituted thiosemicarbazides 1 react with acyl isothiocyanates to give bithioureas 2 , which by the action of sodium ethanolate cyclize to 1,2,4-triazoline-3-thiones 3 and 5 , respectively. Treatment of 2 with methyl iodide yields 1,3,4-thiadiazoline-2-imines 8 isomeric with 3 . Compound 8d undergoes a thermal induced DIMROTH rearrangement to give 3d in good yield.     

Synthesis and properties of azoles and their derivatives. 36. Synthesis of 2-amino-1,3,4-oxadiazoles, 2-amino-1,3,4-thiadiazoles,and 1,2,4-triazoline-3-thiones containing indolyl radicals

On the heterocyclization of 1-(indol-3-ylcarbonyl)thiosemicarbazides, depending on the conditions of performing the reaction, either 1,2,4-triazoline-3-thiones, 2-amino-1,3,4-thiadiazoles, or 2-amino-1,3,4-oxadiazoles containing an indolyl residue in position 5 are obtained. 1,2,4-Triazoline-3-thiones and 2-amino-1,3, 4-thiadazoles have also been synthesized by the reaction of the hydrochloride of ethyl indol-3-carboximidate with thiosemicarbazides.For communication 35, see [1].Translated from Khimiya Geterotsilicheskikh Soedinenii, No. 9, pp. 1271–1276, September, 1984.     

Cyclization of 1-substituted-3-thiosemicarbazides to triazole derivatives under alkaline conditions

Under both weakly and strongly alkaline conditions, 1-alkyl-2,5-dithiobiureas (1-alkyl-thiocarbamoyl-3-thiosemicarbazides) form 4-alkyl-5-amino-1,2,4-triazoline-3-thiones and 4-alkyl-1,2,4-triazolidine-3,5-dithiones in varying proportions. 1-Alkoxythiocarbonyl-3-thiosemicarbazides expel hydrogen sulfide under weakly basic conditions to form the corresponding 5-alkoxy-1,2,4-triazoline-3-thiones. In a strongly alkaline environment, however, these alkoxy-thiocarbonyl thiosemicarbazides eliminate alcohol to form the appropriate 1,2,4-triazolidine-3,5-dithiones. 1-Alkoxycarbonyl-3-thiosemicarbazides eliminate alcohol in both weakly and strongly basic media to give 5-thiono-1,2,4-triazolidine-3-ones. Cyclization mechanisms of these thiosemicarbazides are postulated.     

Synthesis of Trifluoroalkyl- and Fluoroaryl-Substituted 4,5-Dihydro-1H-1,2,4-triazole-5-thiones

Reactions of 4-(4-fluorophenyl)-, 4-(4-trifluoromethoxyphenyl)-, 4-(3,4-difluorophenyl)-, 4-(4-trifluoromethylphenyl)-, 4-piperidino-, and 4-(3-pyridyl)thiosemicarbazides with esters gave the corresponding 3,4-disubstituted 4,5-dihydro-1H-1,2,4-triazole-5-thiones and their S-alkyl derivatives. Analogous reactions with methyl 2,2,3,3,4,4,5,5-octafluoropentanoate and 2,2,3,3,4,4,5,5-octafluoropentanenitrile afforded, respectively, the acylation and addition products.     

Pyrimidines. XXXIII. Synthesis and properties of new fervenulin derivatives

A series of new 3-substituted fervenulin (6,8-dimethylpyrimido[5,4-c]-1,2,4-triazine-5,7-dione) ( 1 ) derivatives have been synthesized by modifying the 3-alkyl- and aralkyl side-chains. Brominations of 3-methyl -15 , 3-ethyl -16- and 3-benzylfervenulin ( 17 ) led to mono- and dibromo derivatives 22, 23, 25–27 , which are prone to various nucleophilic displacement reactions 24, 28–35 . Periodate oxidation and ozonolysis, respectively, of 3-styrylfervenulin ( 20 ) afforded fervenulin-3-carboxaldehyde ( 36 ) which was transformed to a folic acid analog ( 39 ). Potassium permanganate oxidation of 3-alkylfervenulins 15–19 afforded only ring-contraction to 3-alkyl-5,7-dimethylimidazo[4,5-e]-1,2,4-triazin-6-ones 42–46 which are also formed as mixtures with its 2,4a-dihydro derivatives 47–50 on treatment with ethanolic sodium hydroxide. Fervenulin-3-carboxylic acid ( 55 ) can be converted to the corresponding acid chloride 58 which reacts with amines to fervenulin-3-carboxamides 59, 64–67 and/or 2,4a-dihydro-5, 7 -dimethylimidazo[4,5-e]-1,2,4-triazin-6-one-biscarboxamides 60–64 .     

Direct introduction of heterocyclic residues into 1,2,4-triazin-5(2H)ones

3-Aryl-1,2,4-triazin-5(2H)-ones 1a-c react with indoles 2a-c in trifluoroacetic acid/chloroform or in boiling butanol or acetic acid to give 3-aryl-6-(indolyl-3)-1,6-dihydro-1,2,4-triazin-5(2H)-ones 3a-g . Oxidation of the dihydro-1,2,4-triazin-5(2H)-ones 3a-e afforded 6-(indolyl-3)-1,2,4-triazin-5(2H)-ones 4a-e , products of nucleophilic substitution of hydrogen in 1a-c . Refluxing 1b with N-methylpyrrote 5b in butanol for an extended time resulted in the formation of 3-(4-chlorophenyl)-6-(1-meuiylpyrrolyl-2)-1,2,4-triazin-5(2H)-one 4h. The reaction of 1a-c with indoles 2a-c , pyrroles 5a,b , 1,3-dimethyl-2-phenylpyrazol-4-one (8) and aminothiazoles 9a,b in acetic anhydride affords the 1-acetyl-3-aryl-6-hetaryl-1,6-dihydro-1,2,4-triazin-5(2H)-ones 6a-s . Reaction of 1a-c with N-methyl-pyrrole 5b in acetic anhydride gives beside the 1:1 addition products 6h-k also the 2:1 addition products 7a-c .     

Dérivés de la dihydro-2,4 triazole-1,2,4 thione-3 et de l'amino-2 thiadiazole-1,3,4 à partir de nouvelles thiosemicarbazones d'esters

A new general synthesis of 4,5-disubstituted 2,4-dihydro-1,2,4-triazole-3-thiones is proposed. These heterocycles are obtained by the action of primary amines, arylhydrazines or aroylhydrazines on the thiosemicarbazones of eaters. These last compounds are prepared by action of chlorhydrates of iminoethers on thiosemicarbazide in dimethylformamide. These thiosemicarbazones react also with strong acids, acid anhydrides and chlorides; by thermolysis and they give 2-amino-1,3,4-thiadiazole derivatives. Also, two derivatives of 1,2,4-triazolo[3,4-b]-1,3,4-thiadiazole have been prepared.     

Synthesis of Spiroheterocycles Containing Thiadiazole Thiadiazine and Triazine Moieties from Nitrilimines

Abstract

A series of 5-substituted 1-methyl-3-phenyl-4,5-dihydro-1,2,4-triazin-6-ones was prepared by the reaction of α-amino acid methyl esters with appropriate nitrilimines and treated with phosphorus pentasulfide to afford 5-substituted 1-methyl-3-phenyl-4,5-dihydro-1,2,4-triazin-6-thiones. When 1,2,4-triazin-6-thiones were allowed to react with nitrilimine, the novel 4,6-dimethyl-2,8-di-phenyl-10-substituted-1-thia-3,4,6,7,9-pentaazaspiro[4.5]dec-2,7-dienes were obtained and confirmed by their elemental analyses and spectral data. Some of the synthesized compounds were tested in vitro for their antimicrobial activity.

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GRAPHICAL ABSTRACT      

Synthesis of some new 4,5-substituted-4H-1,2,4-triazole-3-thiol derivatives

In this study appropriate hydrazide compounds, furan-2-carboxylic acid hydrazide (1) and phenylacetic acid hydrazide (2) were converted into 1,4-substituted thiosemicarbazides 4a-e and 5a-e and 4-amino-5-(furan-2-yl or benzyl)-4H-1,2,4-triazole-3-thiols 7 and 10. The 1,4-substituted thiosemicarbazides were then converted into 5-(furan-2-yl or benzyl)-4-(aryl)-4H-1,2,4-triazole-3-thiols 8a-e and 9a-e. In addition, the azomethines 11a-d and 12a-d were prepared from the corresponding arylaldehydes and the 4-amino-5-(furan-2-yl or benzyl)-4H-1,2,4-triazole-3-thiols 7 and 10. The structures of all the synthesized compounds were confirmed by elemental analyses, IR, (1)H-NMR and(13) C-NMR spectra.     

Synthesis of anhydro-3-mercapto-5-pyrazinyl-1,2,4-triazolium hydroxides

The synthesis of some novel anhydro-3-mercapto-5-pyrazinyl-1,2,4-triazolium hydroxides 5 is described. The appropriate 1-methylhydrazides 3 were condensed with isothiocyanates to give the thiosemicarbazides 4 which were cyclized to 5 under mildly basic conditions. A few 1,2,4-triazole-3-thiones 8 were synthesized for comparison, starting with the 2-methylhydrazides 6 and then carrying out analogous synthetic transformations.     

Facile synthesis of [1,2,4]triazino[4,3-b][1,2,4,5]tetrazepin derivatives by a one-pot reactions using 4-amino-3-hydrazinyl-6-methyl-1,2,4-triazin-5 (4H)-one

<正>4-Amino-3-mercapto-6-methyl-l,2,4-triazin-5(4H)-one 1 converted to 4-amino-6-methy-3-(methylthio)-1,2,4-triazin-5(4H)-one by methylation with methyl iodide.Controlled hydrazination of the resulting compound afforded 4-amino-3-hydrazinyl-6- methyl-l,2,4-triazin-5(4H)-one 2 as a building block,to the synthesis of some novel derivatives of[1,2,4]triazino- [4,3,b][1,2,4,5]tetrazepine 3-6,by the reaction with 3-chloropentane-2,4-dione,chloro acetonitrile,1,3-dichloroacetone,and methyl bromoacetate.This general synthetic procedure can be extended to the preparation of wide variety of tetrazepines using 1,2- bielectrophiles derivatives.     

1,2,4-Trimethyl-1,2,4-triazolidine-3-thiones and 3,4-dimethyl-2-methylimino-1,3,4-thiadiazolidines

The reaction of aldehydes and ketones with 1,2,4-trimethylthiosemicarbazide in chloroform in the presence of CF₃COOH gives the corresponding 1,2,4-triazolidine-3-thiones, which in an excess of trifluoroacetic acid irreversibly and quantitatively recyclize to 2-imino-1,3,4-thiadiazolidine derivatives.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 403–407, March, 1992.     

Palladium-catalyzed cyclization reactions of 3-propargylthio 1,2,4-triazin-5(2h)-ones to thiazolo-1,2,4-triazinones

Selective transformation of 3-propargylthio-1,2,4-triazin-5(2H)-ones ($\text{1}$) to 6-methylene-6,7-dihydro-4H-thiazolo[2,3-c][1,2,4]-triazin-4-ones ($\text{2}$) and 3-methylene-2,3-dihydro-7H-thiazolo[3,2-b]-[1,2,4]triazin-7-ones ($\text{3}$) is performed under the conditions of Pd(II) salt or sodium hydroxide catalysis, respectively.     

A Convenient Synthesis of 1,2,4-Triazolo-1,3,5-triazin-4-ones and 1,2,4-Triazolo-1,3,5-triazin-4-thiones

The imidates derived from 3-aminotriazole 1 react with isocyanates and isothiocyanates to give corresponding 1,2,4-triazolo-1,3,5-triazin-4-ones and 1,2,4-triazolo-1,3,5-triazin-4-thiones in a 60–75% overall yield. If the condensation is realized at r.t., then the intermediate 2 can be isolated.     

Synthesis,reactions and biological evaluation of some 1,2,4-triazine derivatives

6-Substituted benzyl-4-phenyl-3-thioxo-2,3,4,5-tetrahydro-1,2,4-triazin-5-ones 3a-d were prepared and converted into their corresponding 3-methylthio derivatives 4a-d . Reaction of compounds 4a-d with hydrazine hydrate gave the corresponding 4-amino-3-anilino-4,5-dihydro-1,2,4-triazin-5-ones 5a-d . 6-Substituted benzyl-4-phenyl-2,3,4,5-tetrahydro-1,2,4-triazin-3,5-diones 9a-c were synthesized and allowed to react with hydrazine hydrate to give the corresponding 6-substituted benzyl-4-amino-2,3,4,5-tetrahydro-1,2,4-triazin-3,5-diones 10a-c . The biological evaluation of some of these triazines is described. All compounds were screened for antiviral, antibacterial, antimycobacterial, antifungal and antiyeast activity. No important biological activity was found.     

The Microwave-Assisted Dehydrative Cyclization of Thiosemicarbazides Forming Substituted 1,2,4-Triazoles

Different types of 4,5-disubstituted 1,2,4-triazole-3-thiones were prepared by microwave irradiation as well as by a classical method. The beneficial effect of microwave irradiation on the dehydrative cyclization of thiosemicarbazides in different reaction media is described. Our results show that the effect of microwave irradiation on the reaction studied was the shortening of reaction times (from 2–9 h to 2–4 min) and a minor decrease (1–4%) in yields. The structure of the new compounds was established by FTIR, MS, and ¹H NMR spectral data.