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Donald C. Dittmer - One of the best experts on this subject based on the ideXlab platform.
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Synthesis of coumarins, 4-hydroxycoumarins, and 4-hydroxyquinolinones by Tellurium-triggered cyclizations.
The Journal of organic chemistry, 2005Co-Authors: Donald C. Dittmer, Dimitry V. AvilovAbstract:Coumarins, 4-hydroxycoumarins, and 4-hydroxyquinolin-2(1H)-ones can be conveniently prepared by treatment of α-halocarboxylic acid esters of salicylaldehyde, o-hydroxyacetophenone, methyl salicylate, and methyl N-methyl- or N-phenylanthranilates with sodium or lithium telluride. Phenylketene formation competes with cyclization of the α-chlorophenylacetate ester of methyl salicylate as demonstrated by a trapping experiment with benzylamine. Elemental Tellurium may be recovered and reused.
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Conversion of Aziridinemethanol Sulfonate Esters to Allylic Amines via Tellurium Chemistry1
Journal of Organic Chemistry, 1997Co-Authors: Aurora S. Pepito, Donald C. DittmerAbstract:Sulfonate esters of aziridinemethanols are converted to allylic amines by treatment with telluride ion obtained by reduction of Elemental Tellurium. In the course of the reaction, Tellurium(0) is reformed and may be reused, thus removing the need to dispose of a key reagent. The telluride reaction yields optically active allylic amines from optically active aziridinemethanols. In contrast to many ring-openings of aziridines by nucleophiles, activation by an electron-withdrawing substituent on nitrogen is not necessary and is even detrimental.
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Conversion of Aziridinemethanol Sulfonate Esters to Allylic Amines via Tellurium Chemistry(1).
The Journal of organic chemistry, 1997Co-Authors: Aurora S. Pepito, Donald C. DittmerAbstract:Sulfonate esters of aziridinemethanols are converted to allylic amines by treatment with telluride ion obtained by reduction of Elemental Tellurium. In the course of the reaction, Tellurium(0) is reformed and may be reused, thus removing the need to dispose of a key reagent. The telluride reaction yields optically active allylic amines from optically active aziridinemethanols. In contrast to many ring-openings of aziridines by nucleophiles, activation by an electron-withdrawing substituent on nitrogen is not necessary and is even detrimental.
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Tellurium in the “no-solvent” organic synthesis of allylic alcohols
Tetrahedron, 1997Co-Authors: Bin Chao, Yongmei Wang, Donald C. DittmerAbstract:Abstract Elemental Tellurium can be reduced by rongalite (HOCH2SO2Na·2H2O)-KOH in the solid phase by application of ultrasound or by microwave irradiation. Without solvent, the organic substrate (eg sulfonate ester of an oxiranemethanol) is added with further sonication or irradiation to yield the desired organic product (eg allylic alcohols) and Elemental Te which may be recycled. Phase-transfer conditions (water-toluene) also are satisfactory.
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A catlaytic Tellurium process for the transposition of allylic hydroxyl groups and carbon-carbon double bonds
Tetrahedron Letters, 1994Co-Authors: Archana Kumar, Donald C. DittmerAbstract:Abstract As little as 0.1 molar equivalent of Elemental Tellurium in combination with excess (up to 3 molar equivalents) reducing agent (HOCH 2 SO 2 Na·2H 2 O, NaBH 4 , or LiEt 3 BH) effects the telluride-ion mediated transposition of allylic hydroxyl groups and carbon-carbon double bonds that proceeds via the epoxy tosylate. The workup is much more convenient than when a molar equivalent of Tellurium is used.
Ray J. Butcher - One of the best experts on this subject based on the ideXlab platform.
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amidomethylation of Elemental Tellurium synthesis and solid state structures of n substituted amidomethylTellurium iv ii derivatives
Dalton Transactions, 2010Co-Authors: Shafalika Misra, Ashok K.s. Chauhan, Puspendra Singh, Ramesh C. Srivastava, Andrew Duthie, Ray J. ButcherAbstract:Amidomethylation of Te(0) (Elemental Tellurium) as well as Te(II) (arylTellurium bromide, in situ) proceeds readily under mild conditions. It involves oxidative insertion of low valent Tellurium into the C–Br bond of N-substituted α-bromoacetamides and provides a direct synthetic route to the stable, crystalline amidomethylTellurium(IV) dibromides, (RR′NCOCH2)2TeBr2 (RR′N = Et2N (1b), MePhN (2b), Me(c-Hex)N (3b), O(CH2CH2)2N (4b)) and (Et2NCOCH2)ArTeBr2 (Ar = mesityl, 5b; 1-naphthyl, 6b). Biphasic bisulfite reduction of the dialkylTellurium dibromides afforded yellow to orange coloured amido functionalized symmetrical telluroethers, (RR′NCOCH2)2Te (RR′N = Et2N (1), MePhN (2), Me(c-Hex)N (3), O(CH2CH2)2N (4)), of which compound 2 was isolated as a crystalline solid. Oxidation of the new dialkyltelluroethers with dihalogens (Br2, I2) or SO2Cl2 afforded the corresponding amidomethylTellurium(IV) dihalides, (RR′NCOCH2)2TeX2 (RR′N = Et2N, X = Cl (1a), Br (1b), I (1c); RR′N = MePhN, X = Cl (2a), Br (2b), I (2c); RR′N = Me(c-Hex)N, X = Cl (3a), Br (3b), I (3c); RR′N = O(CH2CH2)2N, X = Cl (4a), Br (4b), I (4c)) that were characterized by Elemental analyses and multinuclear (1H, 13C, 125Te) NMR. Single crystal X-ray data on 1b, 1c, 2, 2b, 2c, 4b, 5b and 6b suggest that the N-substituted amidomethyl group acts as a small-bite chelating ligand, via intramolecular 1,4-Te⋯O coordination, towards the Te(IV) centre. Steric congestion around Te(IV) due to intramolecular secondary bonding interaction(s), reduced electrophilicity of Te(II) and the partial positive charge on N due to the resonating character of the amido group presumably prevents these atoms from participating in the intermolecular associative forces in the solid state. Instead, weak C–H⋯O and C–H⋯X H-bonding interactions take centre-stage in the self assembly.
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Amidomethylation of Elemental Tellurium: Synthesis and solid state structures of N-substituted amidomethylTellurium(IV & II) derivatives
Dalton transactions (Cambridge England : 2003), 2010Co-Authors: Shafalika Misra, Ashok K.s. Chauhan, Puspendra Singh, Ramesh C. Srivastava, Andrew Duthie, Ray J. ButcherAbstract:Amidomethylation of Te(0) (Elemental Tellurium) as well as Te(II) (arylTellurium bromide, in situ) proceeds readily under mild conditions. It involves oxidative insertion of low valent Tellurium into the C–Br bond of N-substituted α-bromoacetamides and provides a direct synthetic route to the stable, crystalline amidomethylTellurium(IV) dibromides, (RR′NCOCH2)2TeBr2 (RR′N = Et2N (1b), MePhN (2b), Me(c-Hex)N (3b), O(CH2CH2)2N (4b)) and (Et2NCOCH2)ArTeBr2 (Ar = mesityl, 5b; 1-naphthyl, 6b). Biphasic bisulfite reduction of the dialkylTellurium dibromides afforded yellow to orange coloured amido functionalized symmetrical telluroethers, (RR′NCOCH2)2Te (RR′N = Et2N (1), MePhN (2), Me(c-Hex)N (3), O(CH2CH2)2N (4)), of which compound 2 was isolated as a crystalline solid. Oxidation of the new dialkyltelluroethers with dihalogens (Br2, I2) or SO2Cl2 afforded the corresponding amidomethylTellurium(IV) dihalides, (RR′NCOCH2)2TeX2 (RR′N = Et2N, X = Cl (1a), Br (1b), I (1c); RR′N = MePhN, X = Cl (2a), Br (2b), I (2c); RR′N = Me(c-Hex)N, X = Cl (3a), Br (3b), I (3c); RR′N = O(CH2CH2)2N, X = Cl (4a), Br (4b), I (4c)) that were characterized by Elemental analyses and multinuclear (1H, 13C, 125Te) NMR. Single crystal X-ray data on 1b, 1c, 2, 2b, 2c, 4b, 5b and 6b suggest that the N-substituted amidomethyl group acts as a small-bite chelating ligand, via intramolecular 1,4-Te⋯O coordination, towards the Te(IV) centre. Steric congestion around Te(IV) due to intramolecular secondary bonding interaction(s), reduced electrophilicity of Te(II) and the partial positive charge on N due to the resonating character of the amido group presumably prevents these atoms from participating in the intermolecular associative forces in the solid state. Instead, weak C–H⋯O and C–H⋯X H-bonding interactions take centre-stage in the self assembly.
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room temperature insertion of Elemental Tellurium into the csp3 br and i bonds of α bromo and α iodopinacolone
Organometallics, 2007Co-Authors: Ashok K.s. Chauhan, Puspendra Singh, Arun Kumar, Ramesh C. Srivastava, Ray J. Butcher, Andrew DuthieAbstract:PinacolylTellurium(IV) dihalides, (t-BuCOCH2)2TeX2 (X = Br (1b), I (1c)) and Ar(t-BuCOCH2)TeCl2 (Ar = 1-C10H7 (Np) (2a), 2,4,6-Me3C6H2 (Mes) (3a)), are readily prepared at room temperature by the oxidative insertion of Elemental Tellurium into the Csp3−Br or −I bond of the α-halopinacolone and by the reaction of ArTeCl3 with the pinacolone t-BuCOCH3. The bromides Np(t-BuCOCH2)TeBr2 (2b) and Mes(t-BuCOCH2)TeBr2 (3b) can be prepared by the addition of bromine to the telluride Ar(t-BuCOCH2)Te or of α-bromopinacolone to ArTeBr. Variable-temperature 1H and 13C NMR of the separate signals for the o-Me groups in 3a,b indicate a very high barrier to rotation about the Te−C(aryl) bond. Crystal diffraction data for 1c, 2a−c, and 3b show that intramolecular 1,4-Te···O(C) secondary bonding interactions (SBIs) are retained even in the presence of bulky aryl groups and intermolecular Te···X SBIs are subject to electronic population and steric congestion around the Te(IV) center in the solid state.
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Room-Temperature Insertion of Elemental Tellurium into the Csp3−Br and −I Bonds of α-Bromo- and α-Iodopinacolone
Organometallics, 2007Co-Authors: Ashok K.s. Chauhan, Puspendra Singh, Arun Kumar, Ramesh C. Srivastava, Ray J. Butcher, Andrew DuthieAbstract:PinacolylTellurium(IV) dihalides, (t-BuCOCH2)2TeX2 (X = Br (1b), I (1c)) and Ar(t-BuCOCH2)TeCl2 (Ar = 1-C10H7 (Np) (2a), 2,4,6-Me3C6H2 (Mes) (3a)), are readily prepared at room temperature by the oxidative insertion of Elemental Tellurium into the Csp3−Br or −I bond of the α-halopinacolone and by the reaction of ArTeCl3 with the pinacolone t-BuCOCH3. The bromides Np(t-BuCOCH2)TeBr2 (2b) and Mes(t-BuCOCH2)TeBr2 (3b) can be prepared by the addition of bromine to the telluride Ar(t-BuCOCH2)Te or of α-bromopinacolone to ArTeBr. Variable-temperature 1H and 13C NMR of the separate signals for the o-Me groups in 3a,b indicate a very high barrier to rotation about the Te−C(aryl) bond. Crystal diffraction data for 1c, 2a−c, and 3b show that intramolecular 1,4-Te···O(C) secondary bonding interactions (SBIs) are retained even in the presence of bulky aryl groups and intermolecular Te···X SBIs are subject to electronic population and steric congestion around the Te(IV) center in the solid state.
Thomas G. Chasteen - One of the best experts on this subject based on the ideXlab platform.
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Simple, Fast, and Sensitive Method for Quantification of Tellurite in Culture Media
Applied and environmental microbiology, 2010Co-Authors: Roberto C. Molina, Thomas G. Chasteen, Radhika Burra, José M. Pérez-donoso, Alex O. Elías, Claudia M. Muñoz, Rebecca A. Montes, Claudio C. VásquezAbstract:A fast, simple, and reliable chemical method for tellurite quantification is described. The procedure is based on the NaBH(4)-mediated reduction of TeO(3)(2-) followed by the spectrophotometric determination of Elemental Tellurium in solution. The method is highly reproducible, is stable at different pH values, and exhibits linearity over a broad range of tellurite concentrations.
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Production of dimethyl telluride and Elemental Tellurium by bacteria amended with tellurite or tellurate
Applied Organometallic Chemistry, 2001Co-Authors: Rukma S. T. Basnayake, Janet H. Bius, Osman M. Akpolat, Thomas G. ChasteenAbstract:The purpose of this study was to determine whether a facultative anaerobe, Pseudomonas fluorescens K27, would produce dimethyl telluride when anaerobic cultures were amended with differing concentrations of sodium tellurate and/or sodium tellurite and how that volatile organoTellurium production varied over time. Batch bacterial bioreactor experiments were undertaken in order to observe the changes in the headspace of a growth medium solution inoculated with P. fluorescens and amended with Tellurium salts. Gas samples were taken from the bioreactor every hour and were analyzed by capillary gas chromatography using fluorine-induced chemiluminescence detection to determine compounds in the headspace. Liquid samples were analyzed by spectrophotometer to determine optical densities, which were used as an indicator of cell growth. Verification of the identity of the dimethyl telluride produced in the bacterial headspace above a tellurate-amended culture was achieved by comparison with the chromatographic retention time of an authentic (CH3)2Te standard and by gas chromatography/mass spectrometry. The time course production of dimethyl telluride varied with amendment salts' Tellurium oxidation states and concentrations. Increasing tellurate concentrations caused slower bacterial growth, but those cultures reached the stationary phase sooner than cultures amended with tellurite concentrations 10 or 100 times less. Black Elemental Tellurium (Te0) was produced by live cultures amended with Tellurium salts but not by sterile controls. The amount of Tellurium in the solid phase (as Te0 and in/or on cells) harvested from replicate, anaerobic cultures of P. fluorescens sampled after 92 h of incubation was approximately 34%. Mixed tellurite/tellurate amendment experiments exhibited a synergistic toxic effect and yielded less final biomass and very little dimethyl telluride production compared with cultures amended with either tellurate or tellurite alone. Copyright © 2001 John Wiley & Sons, Ltd.
John M Winfield - One of the best experts on this subject based on the ideXlab platform.
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oxidation of Tellurium by molybdenum and uranium hexafluoride in acetonitrile and reactions between uranium hexafluoride and dichlorine or hydrogen chloride in acetonitrile
Journal of Fluorine Chemistry, 1992Co-Authors: Laurence Mcghee, John M WinfieldAbstract:Abstract Reactions between Elemental Tellurium and UF6 or MoF6 at room temperature lead to the isolation of solid products formulated as [TeIVF3(NCMe)2][MVF6][MVF5(NCMe)]3 (MMo or U) on the basis of their spectroscopic properties. In contrast, oxidation of Te by SbF5, AsF5 or the [NO]+ cation in MeCN appears to be limited to the formation of the [Te4]2+ cation. Uranium hexafluoride is reduced to [UF5(NCMe)] in the presence of Cl2 or HCl in MeCN, the reduction being followed by Cl-for-F exchange to give [UF5−xClx(NCMe)] mixtures. A rationalization of these reactions is presented.
Yoshihiro Iwasa - One of the best experts on this subject based on the ideXlab platform.
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pressure induced topological phase transition in noncentrosymmetric Elemental Tellurium
Proceedings of the National Academy of Sciences of the United States of America, 2019Co-Authors: Toshiya Ideue, Motoaki Hirayama, Hiroaki Taiko, Takanari Takahashi, Masayuki Murase, Takashi Miyake, Shuichi Murakami, T Sasagawa, Yoshihiro IwasaAbstract:Recent progress in understanding the electronic band topology and emergent topological properties encourage us to reconsider the band structure of well-known materials including Elemental substances. Controlling such a band topology by external field is of particular interest from both fundamental and technological viewpoints. Here we report possible signatures of the pressure-induced topological phase transition from a semiconductor to a Weyl semimetal in Elemental Tellurium probed by transport measurements. Pressure variation of the periods of Shubnikov–de Haas oscillations, as well as oscillation phases, shows an anomaly around the pressure theoretically predicted for topological phase transition. This behavior is consistent with the pressure-induced band deformation and resultant band-crossing effect. Moreover, effective cyclotron mass is reduced toward the critical pressure, potentially reflecting the emergence of massless linear dispersion. The present result paves the way for studying the electronic band topology in well-known compounds and topological phase transition by the external field.