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The antioxidant activity of pyridylselenium compounds has been evaluated by 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical and nitric oxide (NO) scavenging methods. Pyridylselenium compounds have shown far superior (100-1000 times) antioxidant property than ebselen. The control release of bis(2-pyridyl) diselenide from poly(acrylamide) hydrogels has been studied in order to evaluate its release mechanism and diffusion coefficient. The later study also demonstrates that the pyridylselenium loading into the polymer matrix increases the magnitude and the rate of the radical scavenging activity of the poly(acrylamide) hydrogels. Copyright

A number of methyl substituted 2,2′-dipyridyl diselenides and -ditellurides have been prepared. Effect of the solvent and the substituents on the rate of these reactions have also been studied. The preparation of 2-methylseleno/telluro picolines by reductive cleavage of the diselenides and ditellurides and by one pot reaction using n-BuLi at -78°C in THF is reported.

Synthesis of 2,2′-dipyridyl diselenide/ditelluride and some alkyl/aryl pyridyl selenide/telluride is reported.

Regioselective synthesis of a novel family of water-soluble 2H,3H-[1,3]chalcogenazolo[3,2-a]pyridin-4-ium derivatives was developed based on 2-pyridinesulfenyl and -selenenyl halides and unsaturated compounds. The annulation reactions with divinyl sulfide

Various 2,2′-dipyridyl diselenides were prepared by a simple and convenient method employing non-cryogenic conditions. The diselenide anion, Se22- formed by reducing elemental selenium with 100% hydrazine hydrate in sodium hydroxide reacts in situ with 2-bromopyridines to afford the title compounds in good to excellent yields. Hydrazine hydrate readily cleaves the selenium-selenium bond in these diselenides to generate 2-pyridylselenolate anion, which reacts with halomethanes to afford 2-pyridylseleno methanes. X-ray crystal structure of 4,4′-dimethyl-2,2′-dipyridyl diselenide (4) and tris(2-pyridylseleno)methane (10) is described.

Numerous human diseases are linked to a biochemical condition known as oxidative stress (OS). Antioxidants are therefore becoming increasingly important as potential disease prevention and therapeutic agents. Since OS is a multi-stressor event, agents combining a range of different antioxidant properties, such as redox catalysis and metal binding, might be more effective and selective than mono-functional agents. Selenium derivatives of aniline and pyridine combine redox activity with metal binding properties. These multifunctional agents have a distinct electrochemical profile, and exhibit good catalytic activity in the glutathione peroxidase mimic and metallothionein assays. They also show antioxidant activity in a skin cell model of UVA-induced stress. These compounds might therefore provide the basis for novel agents combining two or more distinct antioxidant properties. The Royal Society of Chemistry 2005.

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We report a diaryldiselenide catalyst for cross-dehydrogenative nucleophilic functionalization of hydrophosphoryl compounds. The proposed organocatalytic cycle closely resembles the mechanism of the Atherton-Todd reaction, with the catalyst serving as a recyclable analogue of the halogenating agent employed in the named reaction. Phosphorus and selenium NMR studies reveal the existence of a P-Se bond intermediate, and structural analyses indicate a stereospecific reaction.

This report describes the synthesis of organoselenyl isoquinolinium imides through a tandem cyclization betweenN′-(2-alkynylbenzylidene)hydrazides and diselenides. The reaction was carried out at room temperature under an ambient atmosphere using cheap iron(iii) chloride as the metallic source. The strategy shows good tolerance to a broad range ofN′-(2-alkynylbenzylidene)hydrazides and diselenides, and forms C-N and C-Se bonds in one step. The obtained product is further transformed into a bioactiveH-pyrazolo[5,1-a]isoquinoline skeleton easilyviaa silver catalyzed [3 + 2] cycloaddition.

A new protocol was developed to synthesize (enantioenriched) thioethers and selenoethers from (chiral) benzylic trimethylammonium salts and di(hetero)aryl disulfides or diselenides. These syntheses were promoted by the presence of weak base and did not require the use of any transition metal, and resulted in the target products with good to excellent yields (72-94%). Using quaternary ammonium salts synthesized from enantiomerically enriched amines led to highly enantiopure benzylic thioethers and selenoethers (94-99% ee) with configurations reversed from those of their enantioenriched quaternary ammonium salts. This journal is

The rearrangement of selenium ylides is even today almost unexplored, although it would provide access to important organoselenium compounds with broad downstream applications. In this report, the first systematic study of sigmatropic rearrangement reactions of selenium ylides using a simple rhodium catalyst with catalyst loadings as low as 0.01 mol % is described. Selenium oxide pyrolysis of the rearrangement products gives access to important 1,1-disubstituted butadienes.

We describe here an alternative method to prepare bis(2-pyridyl) diselenide derivatives using reduced selenium species, generated in situ, and different 2-chloropyridines promoted by p-TSOH in PEG-400 as solvent. This is a straightforward protocol to prepare bis(3-amino-2-pyridyl) diselenides unprecedented to date. Still, this article describe the employment of synthesized bis(3-amino-2-pyridyl) diselenide and a diverse array of aryl aldehydes to afford the corresponding 2-aryl-selenazolo[5,4-b]pyridines in satisfactory yields and, in a short reaction time under basic condition. Furthermore, when the bis(3-amino-2-pyridyl) diselenide reacted with aliphatic halides, in the presence of NaBH4, a wide range of unsymmetrical diorganyl selenides was obtained. To complete this investigation the bis(3-amino-2-pyridyl) diselenide was evaluated for its inhibitory effect on the acetylcholinesterase (AChE) activity and free radical-scavenging capacity. Results demonstrated that this compound was antioxidant and inhibitor of the AChE activity, being a promising therapeutic agent for the treatment of Alzheimer's disease and other neurodegenerative disorders.

The reaction of bis(organyl)diselenide with a reducing agent, such as LiAlH4, NaBH4, Li(C2H5)3BH, etc., generally leads to cleavage of the Se-Se bond resulting in the formation of the corresponding organylselenols/selenolates. However, this work for the first time demonstrates the scisson of the C(pyridine)-Se bond in bis(2-pyridyl)diselenides with LiAlH4. The reaction affords analytically pure bis(2-pyridyl)selenides in near quantitative yields. The reaction pathway involves the formation of a selenated aluminato complex followed by the scission of the C(pyridine)-Se bond and generation of LiAlSeH2. The generation of LiAlSeH2 was established by experimental and NMR analysis. The mechanism of the reaction has been supported by theoretical analysis. Single crystal X-ray structure determination of bis(3-methyl-2-pyridyl)selenide (2e) was performed and it shows that the molecules are self-assembled in a 2D-network of C-H?N hydrogen bonds and π?π stacking interactions. The synthesized compounds were also evaluated against the Raji cancer cell line (acute lymphoid leukemia).

A target synthesis of a library of symmetric aromatic diselenides was attempted with the aim of generating anticancer lead compounds. Out of thirteen screened molecules (1-13) against a panel of human cancer cell lines, compound 8 exhibited highest cell growth inhibition in Human leukemia HL-60 cells with IC50 value of 8 μM. Compound 8 had a good pro-apoptotic potential as evidenced from several apoptotic protocols like DNA cell cycle analysis and monitoring of apoptotic bodies formation using phase contrast and nuclear microscopy with Hoechst 33,258. Also, 8 significantly inhibits S phase of the cell cycle and eventually trigger apoptosis in HL-60 cells through mitochondrial dependent pathway substantiated by the loss of mitochondrial potential. A theoretical investigation of DNA binding ability of 8 showed that it selectively bind to minor groove of DNA, where it is stabilized by hydrogen bonding and hydrophobic interactions.

Pyridyl and pyrimidyl based organoselenium compounds have been synthesized and characterized by analytical and spectroscopic techniques. Molecular structures of 2,2′-dipyrimidyl diselenide (1b), 2,2′-dipyrimidyl selenide (2b) and 2-pyrimidyl seleno ethanoic acid (3d) have been determined by single crystal X-ray diffraction analyses. The 3d is associated in the solid state through hydrogen bonding between carboxylic acid proton and N2 of the pyrimidyl ring of an adjacent molecule. The in vitro GPx-like catalytic activity for these compounds was evaluated by 1H NMR and HPLC methods where H2O2 was reduced by dithiothreitol (DTTred) and glutathione (GSH) as a thiol cofactor, respectively, in the presence of catalytic amounts of organoselenium compounds. The electron density around selenium atom (-SeSe- or -Se-) which is reflected by 77Se{ 1H} NMR chemical shifts, has been found to be one of the crucial factors in influencing their overall GPx like activity.

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Scope of the copper catalyzed/mediated selenium-nitrogen coupling reaction has been studied for the synthesis of isoselenazolones. It is noticed that the 2-chloro, 2-bromo-, and 2-iodo-aryl amides substrates can be exploited in the selenium-nitrogen coupling reaction by employing 25-100 mol % of CuI/1,10-phenanthroline (L) and potassium carbonate as a base in DMF. Furthermore, electron rich 2-chloro-arylamides also underwent selenium-nitrogen coupling reaction to give biologically important selenium-nitrogen heterocycles. Also, copper-catalyzed selenium-nitrogen coupling reaction has been meticulously applied for the synthesis of diaryl diselenides having methoxy, amine, and amide functionality from respective aryl iodides in the presence of stoichiometric amount of succinimide as an external Se-N coupling partner.

The present invention relates to a single source metalloorganic precursor compound of the formula: wherein M is selected form the Group 14 elements of Germanium, Tin or Lead; A and R are independently selected from: amide, alkyl having from 1 to 20 carbon atoms, aryl, substituted aryl, or -Q'-2-NR'Ln (n=1-4) wherein L is selected from nothing or a Lewis base ligand; Q and Q' are each independently selected from Group VIa elements of sulfur, selenium, or tellurium; and 2-NR and 2-NR' are each independently selected from N-heterocyclic aryl or its derivatives. Methods of producing these compounds are also disclosed. These precursor materials provide in a single compound the binary, tertiary, or quaternary metals in a ratio to each other that is controllable by a judicious choice of metal atoms and organic substituents. The metal alloys are useful in a variety for electronic applications, particularly in semiconductors and solar energy.

The He I and He II photoelectron spectra of the symmetrical isomers of dipyridyl disulfide and diselenide have been measured and interpreted in terms of a composite-molecule model.The sequence of the lowest valence ionisation energies is assigned as: (?8 - nx)- >/- (?7 - nx)+ > nN ca. nN > (?6 - δnx) ca. (?5 - δnx) > (?4 + nx)- >/- (?3 + nx)+, which is consistent with He I/He II photoionisation crosssection ratios, a composite-molecule model and correlations with the assignment of the dimethyl chalcogenides and chalcogenobispyridines, but contrary to STO-3G* and extended valence basis set calculations.Key words: Chalcogenobispyridines; conformational analysis; photoionization.

The reduction of selenium with lithium in THF in the presence of diphenylacetylene as a catalyst afforded lithium diselenide, which reacted with electrophiles giving alkyl or aryl diselenides 1 - 3 and selenides 4, as by-products.The useful method for preparation of diselenides based on this reaction was elaborated.

α-(2-Pyridylseleno) carbonyl compounds (A) were prepared by the reaction of ketones or aldehydes with 2-pyridylselenenyl bromide under various conditions (acidic, basic, or after conversion to silyl enol ethers) in good to excellent yields.Oxidation of A thus prepared affords α,β-unsaturated carbonyl compounds in excellent yields even in the cases where satisfactory results were not obtained by the oxidation of the corresponding α-phenylseleno carbonyl compounds.These results indicate that the 2-pyridylseleno group is a better leaving group than the phenylseleno group in selenoxide elimination leading to enones.

Sodium pyridyl (8b)/isoquinolinyl (8c) selenates on treatment with ethyl chloroacetate give ethyl 2,2'-diselenobis(acetate) (9) and the corresponding carboxamides, but sodium quinazolinylselenate (8a) forms ethyl 2-(4-quinazolinylseleno)acetate (6a) and ethyl 2-acetate (12).With chloroacetonitrile, 8a-c form condensed mesoionic selenazoles, 3-aminoselenazolequinazolin-4-ium hydroxide inner salt (14a), 3-aminoselenazolepyridinium hydroxide inner salt (14b) and 3-aminoselenazoleisoquinolinium hydroxide inner salt (14c) respectively.

The dipole moments of di-2-pyridyl dichalcogenides in benzene solution at 25 and 45 deg C and the HeI photoelectron spectra of di-2-pyridyl and diphenyl dichalcogenides R2X2 (X=S, Se, or Te) were investigated to obtain information about the conformation of these molecules in solution and in the gas phase.The calculated C-X-X-C dihedral angles (100 - 110o) for the dipyridyl dichalcogenides, for wich μcalc=μexp' are at least 10o larger than those for the diphenyl derivates.These result indicate that the ?-interactions between the X atoms and the pyridyl groups are more effective than between the X atoms and the phenyl rings, reducing, as a consequence, repulsion between the lone electron pairs of the chalcogen (X) atoms lowering the torsional barriers about the X-X bonds.The variations of the dihedral angles between the phenyl derivates and the corresponding dipyridyl dichalcogenides as derived on the basis of photoelectron spectroscopic data, is in disagreement with the results from dipole moment data.This difference between the gas phase and solution results may be caused by solvent and temperature effects or by secondary interactions between the ? and ? orbitals.The dipole moment and photoelectron spectral data indicate that the diaryl dichalcogenates are conformationally flexibile with a skew equilibrium conformation and very little interaction between the two aryl groups.

Alkyl pyridyl selenides are oxidized by 1.5 equiv. of 30percent H2O2 in THF to give olefins in good to excellent yields.The yields are always higher than the case where alkyl phenyl selenides are used under the same conditions.