- Catalytic Synthesis of Methylthiophenes
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The gas-phase reaction of dimethyl disulfide with thiophene over Co/HZSM-5 catalyst in a helium medium under atmospheric pressure at 250–350°C gave a mixture of mono-, di-, tri-, and tetramethylthiophenes with an overall selectivity of 94–96%.
- Mashkina,Khairulina
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p. 1794 - 1797
(2019/03/26)
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- Synthesis and redox potentials of methylated vitamin K derivatives
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We report the synthesis of derivatives of vitamin K3 as well as of vitamins K1 and K2 containing a different number of methyl groups in various positions in order to reduce their redox potentials and to change systematically their steric features. The long aliphatic chain of vitamins K1 and K2 is simulated by an undecyl chain or a methyl group, respectively. The redox potentials of the first reduction step were measured by cyclic voltammetry in DMF. These compounds are relevant for studies of the structure-function relationship of vitamin K dependent enzymes and the investigation of electron transfer reactions in photosynthetic reaction centers.
- Schmid, Ralf,Goebel, Friederike,Warnecke, Andre,Labahn, Andreas
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p. 1199 - 1202
(2007/10/03)
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- Anodic Cyanation of Tetramethylthiophene
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The electrooxidation of tetramethylthiophene in methanol containing sodium cyanide produced 2,5-dihydro-2,3,4,5-tetramethylthiophene-2,5-dicarbonitrile 1 (cis/trans = 0.7) and 2,5-dihydro-5-methoxy-2,3,4,5-tetramethylthiophene-2-carbonitrile 2 (cis/trans = 2.2) in 21 and 25percent yields respectively, together with a small amount of 2-methoxymethyl-3,4,5-trimethylthiophene 3.Treatment of the resultant 2,5-mixed adduct 2 with a small amount of acid induced elimination of a methanol molecule to give 2,5-dihydro-2,3,4-trimethyl-5-methylenethiophene-2-carbonitrile 4a.
- Yoshida, Kunihisa,Takeda, Kazusada,Minagawa, Kikuwo
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p. 1119 - 1120
(2007/10/02)
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- Anodic Methoxylation of 2,5-Dimethyl- and Tetramethyl-thiophene. Formation and Transformation of 2,5-Dimethoxy Adducts
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The electrooxidation of 2,5-dimethyl- and tetramethyl-thiophene in methanol containing sodium methoxide produced isomeric mixtures (in either case 40percent cis, 60percent trans) of the corresponding 2,5-dimethoxy adducts each in 30percent yield, together with side-chain oxidation products.During GLC analysis a portion of the 2,5-dimethoxy adduct of 2,5-dimethylthiophene loses a methanol molecule to give 2,5-dihydro-2-methoxy-2-methyl-5-methylenethiophene.By contrast, the 2,5-dimethoxy adduct of the tetramethyl compound remained intact to GLC.In CDCl3 solution in an NMR tube, each isomer of the 2,5-dimethoxy adducts was transformed into the corresponding 2-(methoxymethyl)thiophene.When sodium acetate was used as electrolyte, the products were the corresponding 2-(methoxymethyl)thiophenes plus thiophene-2-carbaldehydes.In order to synthesize 2-acetoxymethyl-5-methylthiophene as a reference compound, anodic acetoxylation of 2,5-dimethylthiophene was also examined.
- Yoshida, Kunihisa,Takeda, Kazusada,Fueno, Takayuki
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p. 2817 - 2820
(2007/10/02)
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- Thiometalate complexes containing arene, thiophene, and cyclobutadiene coligandls. Are thiometalate clusters good models for desulfurization catalysts?
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Reaction of [(p-cymene)RuCl2]2 and (PPh4)2WS4 gives [(p-cymene)RuCl]2WS4; the corresponding (C6Me6)Ru and (p-cymene)Os derivatives were also prepared. 1H NMR and IR data suggest that these compounds comprise pairs of pseudooctahedral metal centers bridged by the tetrahedral WS4. Related syntheses gave RuRe and Ru2PtW2 compounds from ReS4- and Pt(WS4)22-, respectively. The reaction of (p-cymene)RuCl2(PPh3) and (PPh4)2WS4 gave (p-cymene)RuWS4(PPh3), whose structure was verified by X-ray crystallography. (p-cymene)RuWS4(PPh3) crystallizes in the monoclinic space group P21/c (No. 14) with a = 9.254 (3) ?, b = 15.690 (8) ?, c = 20.102 (9) ?, β = 98.77 (3)°, and Z = 4. The analogous reaction of (tetramethylthiophene)-RuCl2(PPh3) and (PPh4)2WS4 results in the release of free tetramethylthiophene. In contrast, the p-cymene ligands were only labilized by further treatment of [(p-cymene)RuCl]2WS4 with WS42-. [(C4Me4)NiCl2]2 and WS42- give [(C4Me4)NiCl]2WS4 while (C4Me4)NiWS4(PMe2Ph) was prepared from (C4Me4)NiCl2(PMe2Ph). (C4Me4)NiWS4(PMe2Ph) crystallizes in the monoclinic space group Ia (No. 9) with a = 13.294 (6) ?, b = 25.519 (11) ?, c = 13.186 (6) ?, β = 97.44°, and Z = 8. Treatment of [(C4Me4)NiCl]2WS4 with (Me3Si)2S gives a polymeric sulfided material, which upon pyrolysis evolves tetramethylthiophene.
- Howard, Kevin E.,Lockemeyer, John R.,Massa, Mark A.,Rauchfuss, Thomas B.,Wilson, Scott R.,Yang, Xiaoguang
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p. 4385 - 4390
(2008/10/08)
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- An Electron Spin Resonance Study of the Radical Cations of Pyrroles, Furans, and Thiophenes in Liquid Solution
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Photolysis of alkylpyrroles in trifluoroacetic acid containing mercury(II) trifluoroacetate, alkylfurans in trifluoroacetic acid, or alkylthiophenes in sulphuric acid, induces oxidation to the corresponding radical cations.The e.s.r. spectra show that the electronic configuration is similar in all three species, the unpaired electron occupying the φA MO in which the heteroatom lies in a nodal plane.Photolysis of 2,6-dimethyl- and 2,6-diethyl-thiophene in trifluoroacetic acid containing mercury(II) trifluoroacetate, on the other hand, gave rise to spectra with a high g value (2.0062), showing hyperfine coupling to two non-equivalent pairs of alkyl groups in an unsymmetrical dimer.
- Davies, Alwyn G.,Julia, Luis,Yazdi, Safieh N.
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p. 239 - 244
(2007/10/02)
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- Electron-transfer activation of coordinated thiophene: Preparation and desulfurization of (η5-C5Me5)Rh(η4-C 4Me4S)
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Cyclic voltammetry studies show that [(C5Me5)Rh(C4Me4S)]2+ undergoes two reversible one-electron reductions at low potentials. The reduced product was synthesized by cobaltocene reduction and was characterized as [(η5-C5Me5)Rh(η4-C 4Me4S)]. 1H and 13C NMR spectroscopic results are consistent with a symmetrical, reduced thiophene ligand. An X-ray crystallographic study confirms that the reduced complex contains a nonplanar η4-thiophene ligand with an uncoordinated sulfur atom. The reduced complex reacts with Fe3(CO)12 to give (C5Me5)RhC4Me4Fe(CO)3 which is analogous to a major product in the Fe3(CO)12 desulfurization of thiophenes. Electron-transfer activation is proposed to be relevant to the desulfurization of thiophenes by metal surfaces.
- Ogilvy, Ann E.,Skaugset, Anton E.,Rauchfuss, Thomas B.
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p. 2739 - 2741
(2008/10/08)
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- The Electron Spin Resonance Spectra of the Radical Cations of Furans, Thiophenes, and Pyrroles in Liquid Solution
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The radical cations of various furans, thiophenes, and pyrroles have been generated in fluid solution and characterised by e.s.r. spectroscopy.
- Davies, Alwyn G.,Julia, Luis,Yazdi, Safieh N.
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p. 929 - 930
(2007/10/02)
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- REACTION OF FURAN COMPOUNDS WITH HYDROGEN SULFIDE AND ASPECTS OF ITS APPLICATION
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The conversion of α-methylfuran, di-, and polyalkylfurans, and ethers, esters, ketones, and other derivatives of the furan series to the corresponding substituted thiophenes was realized under acid-catalysis conditions.
- Kharchenko, V. G.,Gubina, T. I.,Voronin, S. P.,Markushina, I. A.
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p. 1170 - 1173
(2007/10/02)
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- GENERAL SYNTHESIS OF POLYSUBSTITUTED THIOPHENES FROM DIKETO SULFIDES
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Treatment of diketo sulfides with a low-valent titanium reagent at 0 deg C (in two cases at room temperature) affords 3,4-dihydroxythiolanes in good yields.The acid-catalyzed (p-toluenesulfonic acid) dehydration of the latter compounds leads to the corres
- Nakayama, Juzo,Machida, Haruki,Saito, Ryuji,Hoshino, Masamatsu
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p. 1983 - 1984
(2007/10/02)
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- Rates of the Ring Opening of Some Bicyclic 3-Thienyllithium Derivatives
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The rates of ring opening of some cycloalkane -annellated thienyllithium derivatives have been determined.The cyclopenta system appeared to be several thousand times more reactive than the cyclohepta and cycloocta systems.The rate difference is explained by a considerable ring strain in the five-membered case.
- Frejd, Torbjoern,Karlsson, J. Olle
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p. 895 - 900
(2007/10/02)
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