Organotellurium Research Articles

Synthesis, spectroscopic characterization and structural studies of dialkyl dithiophosphinate and N, N-dialkyl dithio- and monothio-carbamate derivatives of 1-iodo-1,1,2,3,4,5-hexahydrotellurophene

The synthesis of the organotellurium(IV) compounds [C 4H 8TeI(S 2PMe 2)] ( 2), [C 4H 8TeI(S 2PEt 2)] ( 3), [C 4H 8TeI(S 2CNC 4H 6)] ( 4) and [C 4H 8TeI(SOCNC 5H 10)] ( 6) was achieved. All of them were characterized by IR, 1H-, 13C-, 31P- and 125Te-NMR, mass spectroscopy, elemental analyses and single-crystal X-ray diffraction. In addition, the crystal and molecular structures of the previously known 1,1-diiodotetrahydrotellurophene and [C 4H 8TeI(S 2CNEt 2)] ( 5) were obtained. The geometry around Te(IV) is that of a sawhorse structure in which the lone pair is apparently stereochemically active and occupying an equatorial position in a distorted trigonal bipyramid. All the structures exhibit different supramolecular associations. The intermolecular Te⋯S and Te⋯I interactions result in the formation of dimeric species in 4, and in 1 and 6, respectively. The intermolecular Te⋯S bonds in 2, 3 and 5 lead to formation of one-dimensional polymers.

Radical-Mediated Synthesis of Substituted Quinones with Organotellurium Compounds

Abstract Carbon-centered radicals generated from the corresponding organotellurium compounds react with a variety of quinones under photo–thermal conditions to give the monoaddition product in good to excellent yield. The reaction can be used for the synthesis of polyprenyl quinoid natural products.

Novel and general cross-coupling reactions of alkynylzinc reagents and organotellurium compounds

The efficient cross-coupling reactions of different alkynyl organozinc reagents with unsaturated organotellurium species catalyzed by Pd(PPh 3) 4/CuI and using THF/DMF systems are described. These cross-coupling reactions are general and permit the formation of new sp–sp 2 carbon–carbon bonds. New reactions to reach the necessary alkynylzinc intermediates were also developed from terminal alkynes or using acetylenic tellurides as starting materials.

Palladium-catalyzed cross-coupling reactions of dimethyl- and diethylzinc with unsaturated organotellurium compounds

The cross-coupling reaction of diethyl- or dimethylzinc compounds with disubstituted vinylic tellurides as electrophilic partners is described. These cross-coupling reactions were catalyzed by Pd(PPh 3) 4/CuI and were shown to be general, allowing the formation of a new sp 3– sp 2 carbon–carbon bond. Good yields and high stereoselectivity were observed in all cases.

Water-Soluble Organotellurium Compounds: Catalytic Protection against Peroxynitrite and Release of Zinc from Metallothionein

The antioxidant properties of a number of water-soluble diorganyl tellurides have been investigated. These organotellurium compounds efficiently protect against peroxynitrite-mediated oxidation of dihydrorhodamine 123, hydroxylation of benzoate, and nitration of 4-hydroxyphenyl acetate. The peroxidation of the zinc storage protein, metallothionein, by tert-butyl hydroperoxide is also catalyzed by the water-soluble organotellurium compounds. As compared to selenium-containing compounds (e.g., ebselen and selenocystamine), some of the tellurides that were tested ¿e.g., 3-[4-(N,N-dimethylamino)benzenetellurenyl]propanesulfonic acid, sodium salt¿ exhibit a significantly higher reactivity in these assays, making them some of the most effective compounds tested thus far. The catalysis of destruction of zinc-sulfur clusters by water-soluble organotellurium compounds could have implications for the bioavailability of zinc in vivo. These compounds might be lead compounds for the development of a new class of water-soluble, tellurium-based antioxidant and zinc-releasing drugs.

Bacterial cytotoxicity and induction of apoptosis in promyelocytic (Line HL‐60) cells by novel organotellurium compounds

AbstractThe increasing importance of tellurium in organic synthesis, in industrial applications, and as a possible component in pesticides means that its introduction into the environment will probably increase in the future. A knowledge of the relative toxicity and the mode of toxic action of tellurium‐containing chemicals is therefore important. The work presented here, using growth‐rate inhibition effects on Pseudomonas fluorescens of two model compounds, telluranthrene and tetrachlorodiphenyl ditelluride, suggests that these compounds are at least as toxic as the relatively well‐known selenium oxyanions, selenate and selenite. Experiments with human promyelocytic (line HL‐60) cells indicate that both the above organotellurium compounds induce a form of cell death called apoptosis, or programmed cell death. The induction of apoptosis occurred in both a time‐ and dose‐dependent manner, as assayed by three different analytical methods: fluorescence microscopy, flow cytometry, and gel electrophoresis. The results indicate that organotellurium compounds may find applicability in the fields of chemoprevention and cancer therapy, similar to organoselenium compounds.

Novel Water-Soluble Diorganyl Tellurides with Thiol Peroxidase and Antioxidant Activity.

Novel water-soluble diaryl tellurides, alkyl aryl tellurides, and dialkyl tellurides carrying sulfopropyl groups were prepared and found to possess potent peroxide decomposing and chain-breaking antioxidative capacity. The dilithium, disodium, dipotassium, and bis-tetramethylammonium salts of bis(4-hydroxyphenyl) telluride (4) were treated with 2.3 equiv of 1,3-propanesultone in aqueous tert-butyl alcohol to give the corresponding salts 5 of bis-O-sulfopropylated diaryl telluride. A variety of diaryl ditellurides were reduced with sodium borohydride in ethanol. Upon addition of propanesultone to the resulting sodium arenetellurolates, the corresponding 3-aryltellurenylpropanesulfonic acid sodium salts 8 were precipitated. Diphenyl diselenide and dibutyl ditelluride reacted similarly to afford the sodium salts of 3-benzeneselenenylpropanesulfonic acid (9) and 4-telluraoctanesulfonic acid (10), respectively. The glutathione peroxidase-like activity of the water-soluble compounds was assessed at pH = 7.4 by using the coupled GSSG reductase assay. Dialkyl telluride 10 turned out to be the most efficient catalyst. Several alkyl aryl tellurides 8 were also more efficient than any of the previously tested organotellurium compounds in this model. Bulky and electron-withdrawing aryl substituents seemed to reduce activity, whereas electron-donating groups enhanced it. Alkyl aryl selenide 9 was void of any catalytic activity. The novel compounds were also assessed by (1)H NMR spectroscopy for their capacity to catalyze the hydrogen peroxide oxidation of N-acetylcysteine in D(2)O under acidic conditions. In the presence of 0.01 mol % of the organotellurium catalyst, the thiol concentration was reduced to 50% within 12 min for the most active catalyst (compound 5b). Although many of the compounds showed high catalytic activity, it was not possible to rationalize their relative efficiency. The capacity of the novel organotellurium compounds to act as a scavengers of 1,1-diphenyl-2-picrylhydrazyl (DPPH) was also investigated. The organotelluriums seem to act primarily as electron donors in their reaction with DPPH. Compounds 8d, 10, and 8b were the most effective scavengers. Bulky or electron-withdrawing aryl substituents caused a reduction in activity, whereas electron-donating ones enhanced it. None of the compounds could match vitamin E in their scavanging capacity.

ChemInform Abstract: A Systematic 125Te NMR Study of Organotellurium Compounds: The Effect of Oxidation States and Substituents.

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Oxidative fluorination of some organoantimony and organotellurium compounds by 2-hydroperfluoropropyl azide

Triphenylantimony and diphenyltellurium are readily oxidatively fluorinated by 2-hydroperfluoropropyl azide, CF 3CHFCF 2N 3, to form appropriate difluorides from moderate to high yields.

A systematic 125Te NMR study of organotellurium compounds: The effect of oxidation states and substituents

125Te NMR spectra of aromatic and aliphatic organotellurium compounds were observed in order to investigate the relationship between the structure and the 125Te NMR chemical shift of the compounds. The 125Te NMR chemical shift of organotellurium compounds is sensitive to the type and size of the substituents (aromatic, aliphatic) and the oxidation state of the Te atom. The chemical shift of halooxatelluranes moved upfield when an electron-withdrawing group was attached to the phenyl group. The observed results could be interpreted in terms of the resonance structures of the halooxatelluranes.

Palladium- and copper-catalyzed cross-coupling and carbonylative cross-coupling of organotellurium compounds with organostannanes

Download options Please wait... Article information DOI https://doi.org/10.1039/A906127D Article type Paper Download Citation Chem. Commun., 1999, 2117-2118 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Palladium- and copper-catalyzed cross-coupling and carbonylative cross-coupling of organotellurium compounds with organostannanes S. Kang, S. Lee and H. Ryu, Chem. Commun., 1999, 2117 DOI: 10.1039/A906127D To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Social activity Tweet Share Search articles by author Suk-Ku Kang Sang-Woo Lee Hyung-Chul Ryu

Iodothyronine Deiodinase Mimics. Deiodination of o,o‘-Diiodophenols by Selenium and Tellurium Reagents

To better understand, and in the extension mimic, the action of the three selenium-containing iodothyronine deiodinases, o,o‘-diiodophenols were reacted under acidic conditions with sodium hydrogen telluride, benzenetellurol, sodium hydrogen selenide, or benzeneselenol and under basic conditions with the corresponding deprotonated reagents. Sodium hydrogen telluride was found to selectively remove one iodine from a variety of 4-substituted o,o‘-diiodophenols, including a protected form of thyroxine (T4). Thus, it mimics the D1 variety of the iodothyronine deiodinases. Sodium telluride was a more reactive deiodinating agent toward o,o‘-diiodophenols, often causing removal of both halogens. Benzenetellurol and sodium benzenetellurolate sometimes showed useful selectivity for monodeiodination. However, the products were often contaminated by small amounts of organotellurium compounds. Sodium hydrogen selenide, sodium selenide, benzeneselenol, and sodium benzeneselenolate were essentially unreactive toward o,o‘-diiodophenols. To gain more insight into thyroxine inner-ring deiodination, substituted 2,6-diiodophenyl methyl ethers were treated with some of the chalcogen reagents. Reactivity and selectivity for monodeiodination varied considerably depending on the substituents attached to the aromatic nucleus. In general, it was possible to find reagents that could bring about the selective mono- or dideiodination of these substrates.

Novel Synthesis of Unsaturated Organoselenium and Organotellurium Compounds Based on Organic Dichalcogenides and Elemental Chalcogens

Novel Synthesis of Unsaturated Organoselenium and Organotellurium Compounds Based on Organic Dichalcogenides and Elemental Chalcogens

Protection against peroxynitrite by selenoproteins.

Cellular defense against excessive peroxynitrite generation is required to protect against DNA strand-breaks and mutations and against interference with protein tyrosine-based signaling and other protein functions due to formation of 3-nitrotyrosine. We recently demonstrated a role of selenium-containing enzymes catalyzing peroxynitrite reduction. Glutathione peroxidase (GPx) protected against the oxidation of dihydrorhodamine 123 (DHR) by peroxynitrite more effectively than ebselen (2-phenyl-1,2-benzisoselenazol-3(2H)-one), a selenoorganic compound exhibiting a high second-order rate constant for the reaction with peroxynitrite, 2 x 10(6) M-1s-1. The maintenance of protection by GPx against peroxynitrite requires GSH as reductant. Similarly, selenomethionine but not selenomethionine oxide exhibited inhibition of rhodamine 123 formation from DHR caused by peroxynitrite. In steady-state experiments, in which peroxynitrite was infused to maintain a 0.2 microM concentration, GPx in the presence of GSH, but neither GPx nor GSH alone, effectively inhibited the hydroxylation of benzoate by peroxynitrite. Under these steady-state conditions peroxynitrite did not cause loss of 'classical' GPx activity. GPx, like selenomethionine, protected against protein 3-nitrotyrosine formation in human fibroblast lysates, shown in Western blots. The formation of nitrite rather than nitrate from peroxynitrite was enhanced by GPx, ebselen or selenomethionine. The selenoxides can be effectively reduced by glutathione, establishing a biological line of defense against peroxynitrite. The novel function of GPx as a peroxynitrite reductase may extend to other selenoproteins containing selenocysteine or selenomethionine. Recent work on organotellurium compounds revealed peroxynitrite reductase activity as well. Inhibition of dihydrorhodamine 123 oxidation correlated well with the GPx-like activity of a variety of diaryl tellurides.

Protection by Organotellurium Compounds against Peroxynitrite-Mediated Oxidation and Nitration Reactions

Diaryl tellurides effectively protect against peroxynitrite-mediated oxidation of dihydrorhodamine 123 (DHR), hydroxylation of benzoate, and nitration of 4-hydroxyphenylacetate (HPA). Bis(4-aminophenyl) telluride offered the most efficient protection against oxidation of DHR induced by peroxynitrite. Protection by this compound was approximately 3 times more effective than that afforded by its selenium analog, bis(4-aminophenyl) selenide, and 11 times more effective than selenomethionine. When peroxynitrite was infused to maintain a steady-state concentration, bis(4-aminophenyl) telluride in the presence of GSH, but neither bis(4-aminophenyl) telluride nor GSH alone, effectively inhibited the peroxynitrite-mediated hydroxylation of benzoate. The inhibition of nitration was most pronounced using bis(4-hydroxyphenyl) telluride, and this compound was ca. 3 times more effective than selenomethionine. Bis(4-aminophenyl) telluride also protected proteins in lysates from human skin fibroblasts from peroxynitrite-mediated nitration of tyrosine residues more effectively than selenomethionine. These data establish a potential biological or pharmacological role of organotellurium compounds in the defense against peroxynitrite.

Antioxidative properties of organotellurium compounds in cell systems

The protective/antioxidative properties of diaryl tellurides were demonstrated in cellular systems of increasing complexity. In the presence of glutathione, bis(4-hydroxyphenyl) telluride (1a), bis(4-aminophenyl) telluride (1d) and bis(2-carboxyphenyl) telluride (1h) reduced by more than 50% t-butyl hydroperoxide-induced cell death in lung fibroblast cultures at concentrations below 2 μM. Bis(2,6-dimethyl-4-hydroxyphenyl) telluride (2b) reduced by more than 50% leukocyte-mediated and phorbol-12-myristate-13-acetate-stimulated damage to Caco-2 cells at 0.1 μM concentration. As judged by their abilities to reduce formation of thiobarbituric acid reactive substances at concentrations close to 1 μM, diaryl tellurides 1a, 1d and 2b protected rat kidney tissue against oxidative damage caused by anoxia and reoxygenation. The organotellurium compounds also offered protection after systemic administration. In the presence of diaryl telluride 2b (0.1–1 μM), the ischemia/reperfusion-induced vascular permeability increase in the hamster cheek pouch was significantly reduced as compared with the control. Some of the most active organotellurium cell protectants were evaluated for their ability to inhibit formation of the inflammatory mediators leukotriene B 4 and interleukin-1β. An inhibitory effect on the secretion of these species was seen for compounds 1a and 2b at or above 10 μM concentrations. The protective effects of diaryl tellurides against t-butyl hydroperoxide-induced cell injury can be ascribed mainly to the peroxide-decomposing, glutathione peroxidase-like capacity of the compounds. The chain-breaking, electron- or hydrogen atom-donating ability of diaryl tellurides seems to be the main reason for their protection against leukocyte-mediated cell damage in Caco-2 cells and in the oxidatively challenged rat kidney and hamster cheek pouch.

Role of organotellurium species in tellurium neuropathy.

Exposure of weanling rats to a diet containing 1% elemental tellurium causes segmental demyelination of peripheral nerve, and an inhibition of squalene epoxidase. This inhibition is thought to be the mechanism of action leading to demyelination. Tellurite appears to be the active inhibitory species in a cell-free system but the active species in vivo is unknown. We examined potassium tellurite (K2TeO3) and three organotellurium compounds for their ability to inhibit squalene epoxidase in Schwann cell cultures and to induce demyelination in weanling rats. K2TeO3 had no effect on squalene epoxidase activity in cultured Schwann cells and caused no demyelination in vivo. All three organotellurium compounds caused inhibition of squalene epoxidase in vitro and caused demyelination in vivo. (CH3)2TeCl2 was the most potent of these compounds and its neuropathy most resembled that caused by elemental tellurium. These data are consistent with the hypothesis that tellurium-induced demyelination is a result of squalene epoxidase inhibition and suggest that a dimethyltelluronium compound may be the neurotoxic species presented to Schwann cells in vivo.

The reactions of heterocyclic organotellurium and selenium compounds with triiron dodecacarbonyl

The reaction of 2-telluraphthalide, C8H6OTe, with [Fe3(CO)12] gave as the major characterised species compound 1, [C6H4CH2TeFe(CO)3]2. An iron atom has inserted into the telluracyclic ring, and it is probable that one co-ordinated CO ligand arises from the initially organic carbonyl group. X-Ray single crystal investigations revealed a dimeric structure containing an Fe2Te2 core. The reaction of 2-telluraphthalic anhydride, C8H4O2Te, with [Fe3(CO)12] gave a known, but unexpected, organic product phthalide, C8H6O2. X-Ray crystallography confirmed its isolation; the main feature of interest is the significant double bond character of C(8)–O(1) at 1.352(4) Å. 2-Selenaphthalic anhydride, C8H4O2Se, gave intractable products on reaction with [Fe3(CO)12], but 2-selenaphthalide, C8H6OSe, on reaction with the carbonyl gave a major product 2, [Fe(CO)3{C6H4CH2SeFe(CO)3}] and a minor product 3, [Fe(CO)2{η6-C6H4CH2SeFe2(CO)6}] which is an intermediate in the formation of 2. Compound 2 was shown by X-ray methods to be very similar to 1 except that the 18 electron rule is satisfied by co-ordination of an Fe(CO)3 moiety, rather than by dimerisation. Compound 3, also studied by X-ray crystallography, differs from 2 mainly in the addition of an η6-bonded Fe(CO)2 moiety, but the selenaferrole ring is more distorted. It is proposed that comparative studies of reactions of selenium and tellurium compounds with [Fe3(CO)12] may assist the development of an understanding of the complex reaction pathways.

Novel Synthesis of Unsaturated Organoselenium and Organotellurium Compounds Based on Organic Dichalcogenides and Elemental Chalcogens

A number of synthetic approaches to unsaturated organoselenium and -tellurium compounds is discussed. The synthesis of unsymmetrical (Z)-1,2-bis(alkylseleno)ethenes from organic diselenides and acetylene as an example of one of these approaches is reported.

1H-{125Te} indirect detection in nuclear magnetic resonance spectra of organotellurium compounds

1H-{125Te} indirect detection in nuclear magnetic resonance spectra of organotellurium compounds