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.     

1,2,3-Selenadiazolyl-1,3,4-oxadiazole, 1,2,3-Thiadiazolyl-1,3,4-oxadiazole and 5-(1,2,3-Thiadiazolyl)-s-triazolo[3,4-b]-1,3,4-thiadiazoles

A series of 5-substituted-2-(4-alkyl or phenyl-1,2,3-thia(or selena)diazol-5-yl)-1,3,4-oxadiazoles were prepared. 5-Substituted-2-(4-phenyl-1,2,3-selenadiazol-5-yl)-1,3,4-oxadiazoles upon pyrolysis afforded the corresponding alkynes. Also, a series of 5-substituted-4-amino-3-(1,2,3-thiadiazol-5-yl)-s-triazoles and 5-(1,2,3-thiadiazolyl)-s-triazolo[3,4-b]-1,3,4-thiadiazoles were prepared.     

Heterocyclic studies. 2. 5-Chloro-1H-1,2,3-triazole-4-carboxaldehydes,preparation and rearrangement reactions

A general procedure for synthesis of 5-chloro-1H-1,2,3-triazole-4-carboxaldehydes 4 and the rearrangement reaction of 4-(N-substituted)iminomethylene-1H-1,2,3-triazol-5-ols 6 into N-substituted-1H-1,2,3-triazole-4-carboxamides 7 are described.     

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.     

Synthesis and reactivity of 5-and 6-hydroxy-benzo[b]furan-2-selenolates

Treatment of 2,4-and 2,5-diacetoxyacetophenone semicarbazones with selenium dioxide gave 4-(2,4-and 2,5-diacetoxyphenyl)-1,2,3-selenadiazoles which were readily deacylated by the action of hydrochloric acid. 4-(2,4-and 2,5-Dihydroxyphenyl)-1,2,3-selenadiazoles thus obtained underwent decomposition in the presence of potassium carbonate in acetonitrile with formation of 5-and 6-hydroxybenzo[b]furan-2-selenolates which were subjected to alkylation.     

4-(2-Hydroxyaryl)-1,2,3-selenadiazoles as Precursors of Benzofuran-2-selenolates

The reaction of selenium dioxide with o-hydroxyacetophenone semicarbazones gives 4-(2-hydroxyaryl)-1,2,3-selenadiazoles which undergo ready decomposition by the action of potassium carbonate to form benzofuran-2-selenolates. The latter can be alkylated with methyl iodide and benzyl chloride and arylated with 2,4-dinitrochlorobenzene. Intermediate formation of 2-(o-hydroxyphenyl)ethyneselenolate during decomposition of 1,2,3-selenadiazoles was proved by the isolation of methyl o-methoxyphenylethynyl selenide when the substrate was treated with potassium carbonate in the presence of methyl iodide.     

Selenium heterocycles. XXX. Synthesis of 4-substituted vinyl 2-thioxo-1,3-dithioles and 5-substituted vinyl 2-thioxo-1,3-thiaselenoles

4-Substituted vinyl and 4-(4-phenyl-1,3-butadienyl)-1,2,3-thiadiazoles were prepared through the reaction of 4-aryl-3-buten-2-one semicarbazone and 6-phenyl-3,5-hexadien-2-one semicarbazone with thionyl chloride, respectively. Decomposition of these 1,2,3-thiadiazoles as well as the corresponding 1,2,3-selenadiazoles with base and subsequent addition of carbon disulfide afforded 4-substituted vinyl 2-thioxo-1,3-dithioles and 5-substituted vinyl 2-thioxo-1,3-thiaselenoles.     

Selenium-sulfur analogs 2. Synthesis and characterization of 4-aralkyl-1,2,3-selenadiazoles and -1,2,3-thiadiazoles

1 The3-diketones 5 and 8 were alkylated with methyl iodide to give the nonenolizable diketones 6 and 9 which condensed with semicarbazide hydrochloride yielding the monosemicarbazones 7 and 10 . Cyclization with selenous acid or with thionyl chloride led to the corresponding 1,2,3-selenadiazoles 3a , 4a , and 1,2,3-thiadiazoles 3b , 4b .     

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.     

A Convenient Approach to 2-Aminobenzo[<Emphasis Type="Italic">b</Emphasis>]chalcogenophenes Based on Copper-Catalyzed Transformation of 4-(2-Bromophenyl)-1,2,3-chalcogenodiazoles in the Presence of a Base and Amines

The reactions of 4-(2-bromophenyl)-1,2,3-thia-and -selenadiazoles with amines in the presence of potassium carbonate and copper(I) iodide afforded 2-aminobenzo[b]chalcogenophenes. The corresponding thiaand selenamides, prepared by interaction of 4-(2-bromophenyl)-1,2,3-thia- and -selenadiazoles with amines in the absence of copper salt, were transformed into 2-aminobenzo[b]chalcogenophenes by the action of potassium carbonate and copper(I) iodide in DMF in different yields.     

Synthesis of Bis(2-benzofuranyl) Diselenides from 4-(2-Hydroxyaryl)-1,2,3-selenadiazoles

4-(2-Hydroxyaryl)-1,2,3-selenadiazoles obtained by the action of selenium(IV) oxide on o-hydroxyacetophenone semicarbazones are readily converted into the corresponding potassium benzofuran- 2-selenolates via reaction with potassium carbonate. Oxidation of potassium benzofuran-2-selenolates with iodine gives bis(2-benzofuranyl) diselenides in good yields.     

Synthesis of some thiadiazoles, selenadiazoles and spiroheterocyclic compounds from their 2,2-dimethyl-benzopyran precursors

New series of 4,4-dimethylbenzopyrano[4,3-d]-1,2,3-selenadiazoles and 4,4-dimethylbenzopyrano-[4,3-d]-1,2,3-thiadiazoles have been synthesized from semicarbazones of chroman-4-one precursors. Some 4-acetyl-2′-acetylamino-2,2-dimethylspiro[chroman-4,5′-2-1,3,4-thiadiazolines] have been synthesized by cyclization of thiosemicarbazones of 2,2-dimethylchroman-4-ones using acetic anhydride. The selected compounds were tested for Phosphotyrosine phosphatase 1B inhibition. Published in Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 775–779, May, 2006.     

Reaction of 1,2,3-Selenadiazoles with Phosphines

Nucleophilic attack of tributyl- and triphenylphosphines on 4-phenyl- and 5-ethoxycarbonyl-4-methyl-1,2,3-selenadiazoles leads to the quantitative formation of selenophosphoranes and substituted acetylenes. The molecular structure of 4-phenyl-1,2,3-selenadiazole was confirmed by X-ray crystallography.     

Facile synthesis of 3-aryl-1-((4-aryl-1,2,3-selenadiazol-5-yl)sulfanyl)isoquinolines

A new series of 1,2,3-selenadiazoles containing an aryl or a 3-arylisoquinoline sulfanyl moiety at carbons 4 and 5, respectively, was prepared by cyclization of the respective semicarbazones in the presence of selenium(II) oxide and tetrahydrofuran at 70–75°C. Semicarbazones required for the reaction were obtained from 2-((3-arylisoquinolin-1-yl)sulfanyl)-1-phenylethanones, I, by a reaction with semicarbazide hydrochloride in ethanol/water mixture and potassium acetate base.     

Molecular rearrangements of 4-iminomethyl-1,2,3-triazoles. Replacement of 1-aryl substituents in 1H-1,2,3-triazole-4-carbaldehydes

The two structural isomers, 4 and 5 , of 1-substituted-4-iminomethyl-1,2,3-triazoles are interconvertible when heated in dimethyl sulfoxide at 80°. The equilibrium position depends on the electronic properties of the R-substituent, favoring 5 for R = alkyl, benzyl and anisyl, and 4 for p-chlorophenyl and p-nitrophenyl. An interesting application is the synthesis of 1-alkyl-1,2,3-triazole-4-carbaldehydes from 1-phenyl-1,2,3-triazole-4-carbaldehyde by Scheme I. The hydrazones 4ij and the oxime 4k do not rearrange due to an unfavorable Z-configuration around the C ? N bond, whereas the acyloximino derivative 4m is converted into the nitrile 11 . The structures of the products have been fully characterized by ¹³C nmr spectroscopy and the mechanistic details of the rearrangement are discussed.     

Expeditious synthesis of new 1,2,3-thiadiazoles and 1,2,3-selenadiazoles from 1,2-diaza-1,3-butadienes via Hurd-Mori-type reactions

Alpha-substituted hydrazones obtained from 1,2-diaza-1,3-butadienes and methylenic or methinic activated substrates gave rise to a wide range of cyclic compounds. In particular, in the presence of thionyl chloride as solvent-reagent, they were transformed into 1,2,3-thiadiazoles,(1) with selenium oxychloride in new 4-substituted 2,3-dihydro-1,2,3-selenadiazoles, while with selenium dioxide, they were transformed into 4-substituted 1,2,3-selenadiazoles. We have also examined the nucleophilic behavior of 1,2,3-thiadiazole 4a in the reaction with 1,2-diaza-1,3-butadienes that produced, under basic conditions, 4-hydrazono-1-(1,2,3-thiadiazolyl)pentane derivatives. This event represents an interesting example of stereoselective synthesis because it leads exclusively to the formation of the RR/SS racemic mixture. These latter compounds, treated with thionyl chloride, gave the corresponding 1,3-di-1,2,3-thiadiazolylpropane derivatives, while with sodium methoxide they afforded 1,2,3-thiadiazolyl-2-oxo-2,3-dihydro-1H-pyrrole systems.     

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.     

Ring transformation of 5-aroyl-3(2H)-isothiazolones to 1,2,5-oxathiazole and 1,2,3-thiadiazole derivatives

Reaction of 2-substituted-5-aroyl-3(2H)-isothiazolones 2 with hydroxylamine and phenylhydrazine was found to give (N-substituted-carboxamido)methylene derivatives of 1,2,5-oxathiazole and 1,2,3-thiadiazole, 5 and 7 , respectively. The formation of these heterocycles was ascribed to a mononuclear heterocyclic rear-rangement of the initially formed ketone derivatives, oximes and hydrazones, through a nucleophilic attack of the = N-OH and = N-NH- groups on the S N bond of the isothiazolone ring. In a similar manner, reaction of isothiazolones 2 with hydrazine was found to give 4-aryl-5-(N-substituted-carboxamido)methyl-1,2,3-thiadiazoles 17 .     

A Theoretical Study on the Tautomerism of C-Carboxylic and Methoxycarbonyl Substituted Azoles

DFT calculations (B3LYP/6-31+G^**) have been carried out on 106 tautomers and conformers of NH-azoles bearing CO₂H and CO₂CH₃ groups. The following azoles systems have been studied: 2-substituted pyrroles, 2-substituted indoles, 2-substituted imidazoles, 2-substituted benzimidazoles, 4(5)-substituted imidazoles, 3(5)-substituted pyrazoles, 3-substituted indazoles (1H and 2H), 3,4(5)-substituted-1,2,3(5)-triazoles, 2,3(5)-substituted-1,2(3),4-triazoles, 4(5)-1,2,3,4(5)-tetrazoles. In the case of pyrazole, 3,5-disubstituted derivatives have also been computed, including four dimers.Dedicated to our friend Professor Vladimir I. Minkin on his 70th anniversary.     

Materials Chemistry of 1,2,3-Selenadiazoles

Abstract

The organic chemistry of 1,2,3-selenadiazoles has been explored to a greater extent due to the fact that the chemistry of 1,2,3-selenadiazoles mostly is driven by its facile decomposition via elimination of a nitrogen molecule and formation of selenaketocarben and/or its dimerization to 1,4-diselenin. The reactions of 1,2,3-selenadiazoles directly with various transition metal compounds have resulted in unique organo-selenium transition metal complexes. However, the materials chemistry of 1,2,3-selenadiazoles has not appeared in literature prior to the first publication on the subject from our laboratory in 2003. To, the best of our knowledge, no research group is engaged in such an activity. We, have exclusively explored the potential of 1,2,3-selenadiazoles for their effective utilization in synthesis of semiconductor nano particles or nano powder and in this lecture, the results and methodology for the same would be discussed.