Reaction of 2-amino-5-aryl-1,3,4-oxadiazoles with compounds with activated double bonds

The reaction of 2-amino-5-aryl-1,3,4-oxadiazoles with unsaturated acids and their chlorides was studied. It was shown by IR spectroscopy and mass spectrometry that acylation with acrylic, methacrylic, and cinnamic acid chlorides takes place at the nitrogen atom of the exocyclic amino group. Depending on the solvent, two reaction pathways are realized with unsaturated acids: acylation of the starting 2-amino-5-aryl-1,3,4-oxadiazole occurs in bromobenzene, while nucleophilic addition to the unsaturated acid molecule is realized in DMF in the presence of potassium hydroxide.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 825–829, June, 1990.     

Reactivity of 2-amino-1,3,4-thiadiazoles. Nucleophilic behaviour of some 2-amino-1,3,4-thiadiazoles: Model compounds

The ambident nucleophilic behaviour of some 2-amino-5-H-1,3,4-thiadiazoles in alkylation, acylation and nitrosation reaction has been verified. The structures assigned to the 2-amino-1,3,4-thiadiazoles ( 1a-i ) and to the Δ²-1,3,4-thiadiazolines ( 2a-e ) agree with the spectral data.     

Selenium heterocycles. XXIV (1). 4-Substituted vinyl and 4-phenyl-1,3-butadienyl-1,2,3-selenadiazoles and related compounds

A series of 4-aryl (or heteroeyclic)-3-buten-2-one semicarbazones as well as 6-phenyl-3,5-hexadien-2-one semicarbazone were reacted with selenium dioxide to give the corresponding 4-substituted vinyl and 4-phenyl-1,2-butadienyl-1,2,3-selenadiazoles. The selenadiazoles were converted to the corresponding 1,4-diselenafulvenes. Pyrolysis of 4-styryl-1,2,3-selenadiazole gave 2,5-distyrylselenophene.     

Selenium heterocycles. XLIII. Syntheses of 3,5-Diaryl-1,2,4-thiadiazoles and 3,5-Diaryl-1,2,4-selenadiazoles

Starting from readily available α-arylsulfonyl-α-bromoacetophenones 2 a series of 3,5-diaryl-1,2,4-thiadiazoles and 3,5-diaryl-1,2,4-selenadiazoles were prepared in moderate yield. Reaction of compounds 2 with thiourea or selenourea gave 2-amino-5-arylsulfonyl-4-phenylthiazole or selenazole in good yield.     

Selenium heterocycles. XXXV . Synthesis and pyrrolysis of aryloxy-, arylthio-, and arylseleno-1,2,3-selenadiazoles

A series of 4-substituted-5-arylthio-1,2,3-selenadiazoles, 4-substituted-5-arylseleno-1,2,3-selenadiazoles and 4-aryloxymethyl-1,2,3-selenadiazoles were synthesized. Pyrrolysis of these compounds afforded the corresponding acetylenes XI, XIII (X = S, Se) and XII, respectively. Oxidation of 4-substituted-5-arylthio-1,2,3-selenadiazoles (XIV) with m-chloroperbenzoic acid gave 4-substituted-5-arylsulfinyl-1,2,3-selenadiazoles (XV) and 4-substituted-5-arylsulfonyl-1,2,3-selenadiazoles (XVI).     

Cyclic condensations of 2-amino-1,3,4-thiadiazole with 1,3-dicarbonyl compounds

The reactions of 2-amino-1,3,4-thiadiazole with 1,3-dicarbonyl compounds are described. 2,4-Pentanedione gave 2-thiocyanato-4,6-dimethylpyrimidine while diethylmalonate and ethyl acetoacetate yielded 5-hydroxy-7H-1,3,4-thiadiazolo[3,2-a]pyrimidin-7-one and 7-methyl-5H-1,3,4-thiadiazolo[3,2-a]pyrimidin-5-one, respectively. The structure of the latter compound was confirmed by a synthesis of the alternative isomeric structure (5-methyl-7H-1,3,4-thiadiazolo[3,2-a]pyrirnidin-7-one) from 2-amino-1,3,4-thiadiazole and α-bromocrotonic acid.     

Modification of biologically active amides and amines with fluoro-containing heterocycles 5. Fluoro-containing heterocyclic derivatives of 2-amino-1,3,4-thiadiazoles

An approach to modification of biologically active 2-amino-1,3,4-thiadiazoles with fluoro-containing five-membered heterocycles was proposed. The approach involves reactions of imines (generated in situ from 2-amino-1,3,4-thiadiazoles and methyl trifluoropyruvate) with 1,3-binucleophiles such as 6-aminouracils, 6-aminothiouracils, N-substituted 3-aminocyclohexenones, N-substituted ureas, N-substituted benzamidines, and 3-aminocrotononitrile.     

Selenium heterocycles. XXXVII . Synthesis of 4-(thiazol-4-yl)-1,2,3-selenadiazoles and 4-(selenazol-4-yl)-1,2,3-selenadiazoles

Starting from readily available 2-substituted-4-formylthiazoles and selenazoles, a series of 4-(2-aryl-4-selenazolyl)-1,2,3-selenadiazoles I and 4-(2-substituted-4-thiazolyl)-1,2,3-selenadiazoles II were prepared. Pyrolysis of compound II afforded (2-substituted-4-thiazolyl) acetylenes VII. Addition of potassium hydroxide pellets to an alcoholic solution of II gave 2-substituted-1,4-diselenafulvenes VIII. Decomposition of compound II with base followed by the addition of carbon disulfide gave 5-substituted 2-thioxo-1,3-thiaselenoles XI.     

Selenium heterocycles XXIII. Synthesis of 4,5-dihydrophenanthro[1,3-d]-1,2,3-selenadiazoles and 10,11 -dihydrophenanthro[1,2-d]-1,2,3-selenadiazoles

The selenium dioxide oxidation of a series of 1,2,3,4-tetrahydrophenanthrone and 1,2,3,4-tetrahydrophenanthren-4-one semicarbazones afforded 4,5-dihydrophenanthro[4,3-d]-1,2,3-selenadiazoles and 10,11-dihydrophenanthro[1,2-d]-1,2,3-selenadiazoles. The latter series which represent a new type of selenaazasteroidal compounds were pyrolyzed and gave the corresponding 1,4-deselenine derivatives.     

Reaction of 2-amino-5-R-phenyl-1,3,4-thiadiazoles with unsaturated acids and acid chlorides

Reaction of 2-amino-5-R-phenyl-1,3,4-thiadizoles with unsaturated acids and acid chlorides in the presence of trimethylamine takes place exclusively at the amino group to form the 2-carboxyalkyl- and 2-acylamino- derivatives, respectively.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 264–267, February, 1990.     

Reaction of 1,2,3-selenadiazoles with boranes

The complex formation of 1,2,3-selenadiazoles with boron trifluoride etherate and phenyldichloroborane has been studied. The molecular structure of the5-ethoxycarbonyl-4-methyl-1,2,3-selenadiazole has been confirmed by X-ray analysis. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 289–293, February, 2007.     

Reactivity of 2-amino-1,3,4-thiadiazoles. Methylation reactions of some 2-amino-5-benzoyl-1,3,4-thiadiazoles

Methylation reactions of 2-amino-5-benzoyl-1,3,4-thiadiazoles 1a-d are reported as a function of alkylating agents (methyl iodide, dimethyl sulfate-potassium carbonate, diazomethane, dimethyl-sulfate-sodium methoxide). Methylation occurs at both the ring nitrogen in position 3 and the exocyclic nitrogen atom.     

Acetylenic ketones. Part III . Reaction of acetylenic ketones with nucleophilic sulfur compounds

Aroylphenylacetylenes reacted with ammonium dithiocarbamate and ammonium hydrogen sulfide in 60% dioxane-waler mixture at 15° to give mainly a mixture of the corresponding β-hydroxy-α-thiobenzoylstyrene derivatives (III) and (E,Z)-β,β'-di(α-aroylstyryl) sulfides (IV), whereas with sodium xanthate and sodium sulfide they gave only (III). However, when benzoyl-(Ia) or p-ehlorobenzoyl-(Id)phenylacetylenes was refluxed with ammonium dithiocarbamate in ethyl alcohol, it gave a mixture of (IIIa or d) and the (E,E)-β,β'-di(α-aroylstyryl) sulfide (VIa or d). β-Hydroxy-α-thiobenzoylstyrene derivatives (III), (E,Z)-(IV) and (E,E)-(VI)-β,β'-di(α-aroylstyryl) sulfides reacted with hydrazine hydrate and phenylhydrazine to give 3(5)-aryl-5(3)-phenyl-(IX)- and 5-aryl-1,3-diphenyl-(X)pyrazoles, respectively. The former compounds (III) reacted with guanidine and ethyl hydrazinecarboxylate to give the corresponding aminopyrimidines (XIII) and acetophenone-N-ethoxycarbonyl hydrazones (XI), respectively.     

Reaction of 2-arylidene-5-methylcyclopentane-1,3,4-trione with β-aminovinylcarbonyl compounds

A simple method is proposed for the synthesis of the previously unknown 2,6,6-trimethyl-9-phenyl-4,5,6,7,8,9-hexahydrobenz[f]-4-azaindane-1,3,8-triones, 2,5-dimethyl-6-R-7-phenyl-4,7-dihydro-4-azaindane-1,3-diones, and their derivatives from 2-arylidene-5-methylcyclopentane-1,3,4-trione and-aminovinylcarbonyl compounds.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 632–636, May, 1971.