Protection against peroxynitrite-mediated nitration reaction by intramolecularly coordinated diorganoselenides

A series of intramolecularly Se center dot center dot center dot X (X = N, O) coordinated diorganoselenides and sulfides are synthesized by using the heteroatom-directed lithiation route and characterized by multinuclear (H-1, C-13, Se-77) NMR, IR spectroscopy, and electrospray mass spectrometry (ES-MS). The intramolecular Se center dot center dot center dot O interactions in diorganoselenides 26-31 have been studied by multinuclear NMR studies in solution and in the solid state by single-crystal X-ray crystallography. The protection against peroxynitrite-mediated nitration reaction (PN assay) by diorganoselenides/-sulfides (with and without intramolecular coordination) has been evaluated. The PN assay data of diorganoselenides reveal that the selenides 20-22, having a basic amino group (sp(3)-N donor) in close proximity of selenium, are more active compared to the diorganoselenides 16-19, having an imino group (sp(2)-N donor), and also show much higher protective action than the unsubstituted diorganoselenides 14 and 15. The diorganoselenides 16-31 were oxidized to corresponding selenoxides 44-59. The redox properties of the selenoxides 13 and 44-59 have been investigated by cyclic voltammetry and potentiometric titration experiments. Two redox potentials for in situ-generated ferrocenyl selenoxides (50, 54-59) were observed. The reduction of selenoxides 13 and 48 to ebselen (2) and selenide 20 with benzenethiol (PhSH) was monitored by ES-MS

Synthesis and characterization of [2-(2-phenyl-5,6-dihydro-4H-1,3-oxazinyl)] tellurenyl chloride

The synthesis and characterization of the first examples of two tellurium compounds based on 2-phenyl-5,6-dihydro-4H-1,3-oxazine substrate are described. Intramolecular (TeN)-N-... interaction in [2-(2-phenyl-5,6-dihydro-4H-1,3-oxazinyl)] tellurenyl chloride is established by single X-ray crystallography. (c) 200

Synthesis, reactivity, electrochemical and crystallographic studies of diferrocenoyl diselenide and ferrocenoyl selenides

Diacyl diselenide (8), diacyl selenide (9) and acyl selenol esters (10-12) incorporating the ferrocenoyl substituent have been synthesized from ferrocene carboxylic acid (13). The new compounds (8-10) have been characterized by multinuclear NMR (H-1, C-13, Se-77), IR spectroscopy and electrospray mass spectrometry. All compounds (8-13) undergo a one electron reversible oxidation at significantly more positive potential than ferrocene. The structures of the diselenide and selenide (8 and 10) have been confirmed by single crystal X-ray diffraction. The absolute structure parameter of 8 indicates that it crystallizes in an enan-tiomerically pure form. The peroxidase-like activities of the diselenide (8) and selenides (9-12) have been determined by the thiol assay. (C) 200

Synthesis of diaryl selenides using the in situ reagent SeCl2

Reactions of in situ prepared SeCl2 With Grignard reagents (prepared from bromobenzene, o-tolyl bromide, 2,6-dimethyl-4-tert-butyl-l-bromobenzene, and 1-bromo-2-methylnaphthalene) and dilithiated benzamides (prepared from N-phenyl, N-cyclohexyl, and N-isopropyl benzamide) are described. (C) 200

Synthesis and characterization of a novel chiral azomethine diselenide

The first chiral diselenide 9 having an ortho-azomethine functional group has been synthesized by the reaction of bis(o-formylphenyl) diselenide with the chiral amine R(+)-(1-phenylethylamine). The chiral diselenide 9 was further characterized by derivatizing it into the corresponding selenenyl halides. The derivatives are characterized by single crystal X-ray diffraction studies. In the solid state, the bromide derivative 11 shows the strongest (SeN)-N-... intramolecular interaction. The chiral azomethine diselenide 9 has been further reduced to afford the diselenide 13. The monoselenide analogues of 9 and 13 have also been synthesized. (c) 200

Influence of both steric effects and te center dot center dot center dot n intramolecular nonbonded interactions on the stabilization of organotellurium compounds incorporating [2-[1-(3,5-dimethylphenyl)-2-naphthyl]-4,5-dihydro-4,4-dimethyloxazole]

A series of novel low-valent organotellurium compounds incorporating [2-[1-(3,5-dimethylphenyl)-2-naphthyl]-4,5-dihydro-4,4-dimethyloxazole] (1) stabilized by (TeN)-N-... nonbonded interactions have been synthesized. The synthesis has been achieved by the ortholithium route. The lithium arenetellurolate 3 was obtained by direct metalation of 1 with 1.6 M of n-BuLi in hexane followed by the insertion of tellurium into the Li-C bond. Oxidation of 3 then afforded the desired ditelluride 4. The reaction of 4 with a stoichiometric amount of sulfuryl chloride yielded stable tellurenyl(II) chloride 5, whereas the addition of an excess sulfuryl chloride led to the formation of tellurium(IV) trichloride 6. The stable bromo compound 7 was obtained by the controlled bromination of 4 with bromine. No tellurium tribromide formation was observed when the ditelluride was treated with an excess of bromine. Compound 4 under-went facile reaction with a stoichiometric amount of iodine to give a stable mono iodo compound (8). The phenyltelluride derivative 9 was obtained by the treatment of lithiated product 2 with PhTeBr at low temperature. Attempts to synthesize the symmetrical telluride of the type R2Te (10) by the reaction of 2 with Te(dtc)(2) (dtc = diethyldithiocarbamate) or TeI2 were unsuccessful. All compounds were characterized by elemental analysis, multinuclear (H-1, C-13, Te-125) NMR, and mass spectrometry techniques. The presence of strong (TeN)-N-... intramolecular nonbonded interactions in all the compounds was confirmed by single-crystal X-ray crystallographic studies

Chelate ring size effect on the reactivity of [2-(2-phenyl-5,6-dihydro-4H-1,3-oxazinyl)]lithium and Se center dot center dot center dot N interactions in low-valent organoselenium compounds: Facile isolation of diorganotriselenide

The reaction of [2-(2-phenyl-5,6-dihydro-4H-1,3-oxazinyl)]lithium (13), containing a six-membered oxazine ring, with elemental selenium gave lithium aryldiselenolate (14) as the major reaction intermediate along with other polyselenolates (15 and 16), whereas [2-(4,4-dimethyl-2-phenyloxazolinyl]lithium (21), containing a five-membered oxazoline ring, on reaction with selenium gave only lithium arlyselenolate 22 under similar conditions. The unusual selenation reaction of aryllithium 13 has been studied by ES-MS spectrometry. The oxidative workup of in situ-generated lithium arylpolyselenolates (14-16) afforded a mixture of diorganopolyselenides (10, 11, 17, and 18), from which diorganotriselenide 11 was obtained as the major product, whereas lithium arylselenolate 22 gave only diselenide 6 on oxidation. Equimolar reactions of diorganotriselenide 11 with sulfuryl chloride and benzenethiol give the novel selenium halide [RSeSeCl (24)] and seleniumselenenyl sulfide (28), respectively. However, the reaction of triselenide 11 with an excess amount of halogenating reagents afforded selenenyl halides [RSeX; X = Cl (25), Br (26), 1 (27)]. The reaction of lithium arylpolyselenolates (14-16) with benzyl chloride gave a mixture of diselenide (10), unsymmetrical diselenide (31), benzyl selenide (32), and dibenzyl diselenide (33). The reaction of 14-16 with a.,W-dibromo-ortho-xylene gave the 10-membered diselenocine (34) and 26. GPx-like activities of diselenide 10 and triselenide 11 have been evaluated by using both benzenethiol and coupled reductase assay methods. Triselenide 11 shows much better GPx-like activity than diselenide 10. Crystal structures of organoselenium compounds (11, 25-27, 29, 32, and 34) were determined by single X-ray crystallography to study the ring size effect of the oxazine ring on Se...N intramolecular interactions

Convenient synthesis, characterization and GPx-like catalytic activity of novel ebselen derivatives

The synthesis and characterization of benzisochalcogenazolones (ebselen derivatives 16-21) is described. The synthesis of 16-21 was achieved by treating the bromo precursors 11-13 with an appropriate dilithium dichalcogenide. The synthesis of benzisoselenazolones 16 and 18 was also accomplished by an alternative route, that is, by treating the corresponding methoxymethyl selenides 22 and 23 with 1 equiv. of bromine. The synthesis of methoxymethyl selenides 22 and 23 was accomplished by lithiation of the bromo precursors followed by treatment with bis(methoxymethyl) diselenide. The benzisoselenazolones 16 and 17 were characterized by single-crystal X-ray techniques. The GPx-like catalytic activities of compounds 16-18 and 21 were determined by using the coupled reductase assay. Compound 16 was found to be less active than ebselen 8 whereas compounds 17 and 18 were more active than ebselen in this assay. Compound 21 showed a 1.5-fold higher activity than its selenium analogue 17. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Structural aspects of some organoselenium compounds

The crystal structures of four organoselenium compounds, viz. bis(2-formylphenyl)diselenide (5), bis(2 -methylnaphthyl)diselenide (6), organoselenenyl sulfide (7), and spiroselenurane (8) are described. Crystal data for 5: space group Pca2(1), crystal system orthorhombic, a = 7.9969(4) angstrom, b = 20.8794(12) angstrom, c = 15.8307(13) angstrom, Z = 8, R = 0.0292. Owing to the presence of a strong Se center dot center dot center dot O interaction in compound 5 the geometry around the selenium atom may be considered as T-shaped. Crystal data for 6: space group Pna2(1), crystal system orthorhombic, a = 18.2253(12) angstrom, b = 13.0714(8) angstrom, c = 7.7355(5) angstrom, Z = 4, R = 0.0570. The molecule has a cisoid conformation. Crystal data for 7: space group Pbcn, crystal system orthorhombic, a = 22.2144(13) angstrom, b = 8.0255(4) angstrom, c = 15.4496(9) angstrom, Z = 8, R = 0.0292. Due to intramolecular Se center dot center dot center dot N interaction in 7 the geometry around selenium is T-shaped. Crystal data for 8: space group P2(1)/c, crystal system monoclinic, a = 7.4585(5) angstrom, b = 19.5634(13) angstrom, c = 8.0428(5) angstrom, P = 97.1320(10)degrees, Z = 4, R = 0.0254. The O - Se - O angle is 172.86(6)degrees

[(CH3)5C5SN(C5H5N)]+ - SYNTHESIS, STRUCTURE AND BONDING

Jutzi P, KOHL F, KRUGER C, WOLMERSHAUSER G, HOFMANN P, STAUFFERT P. [(CH3)5C5SN(C5H5N)]+ - SYNTHESIS, STRUCTURE AND BONDING. ANGEWANDTE CHEMIE-INTERNATIONAL EDITION IN ENGLISH. 1982;21(1):70