- MECHANISM OF RECYCLIZATION OF FURANS TO THIOPHENES AND SELENOPHENES UNDER ACID-CATALYSIS CONDITIONS. 2. KINETIC INVESTIGATIONS OF THE REACTION OF 2,5-DIALKYLFURANS WITH HYDROGEN SULFIDE AND HYDROGEN SELENIDE IN AN ANHYDROUS MEDIUM
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The effect of the concentration of the acidic component on the rates of recyclization of 2,5-dialkylfurans to thiophenes and selenophenes was studied.On the basis of the direct correlation of log k on (H0)I and the isotope effect of the solvent it was established that the reaction proceeds via a mechanism of specific acid catalysis.It was shown that the rates of the reactions with the participation of hydrogen sulfide and hydrogen selenide coincide at equal acidities and temperatures.A scheme for the mechanism of the reaction that includes a step involving the formation of the doubly protonated form of the substrate is proposed.
- Voronin, S. P.,Gubina, T. I.,Trushin, S. A.,Markushina, I. A.,Kharchenko, V. G.
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- New method for synthesis of 2,5-disubstituted thiophenes
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The use of hydrogen sulfide at the moment of formation is proposed for the recyclization of furans into thiophenes in acidic media. The advantages of this method are shown. 1999 KluwerAcademic/Plenum Publishers.
- Gubina,Drevko,Fedina,Rogacheva,Kharchenko
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- Study of the mechanism of recyclization of furans into thiophenes and selenophenes in conditions of acid catalysis. 6. Experiments with labeled atoms. Quantum chemical calculations of intermediates of recyclization and hydrolysis
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The reaction of 2-methyl-5-R-furans (R = Me, Bu, 2,2-pentyl-2-methylpentyl) with H218O was investigated. Furans and the corresponding 2,5-alkanediones containing the 18O isotope were obtained. The general characteristics of the recyclization and isotope exchange reactions were established. A kinetic study of recyclization of 2,5-dimethylfuran with 16O and 18O into 2,5-dimethylthiophene was conducted. A reverse kinetic isotope effect was found. The schemes of the mechanisms of these processes were refined based on the experimental data and quantum-chemical calculations of the recyclization and hydrolysis intermediates. 1998 Plenum Publishing Corporation.
- Gubina,Pankratov,Labunskaya,Voronin,Kharchenko
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- Synthesis of substituted 1,2,4-triazines based on 1,2-bis(2,5-dimethyl-3-thienyl)ethanedione
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A novel, convenient method has been developed for the synthesis of 1,2-bis(2,5-dimethyl-3-thienyl)ethanedione, from which were prepared 5, 6-bis(2,5-dimethyl-3-thienyl)-1,2,4-triazines (analogs of the photochromic 1,2-diarylethenes). The principial possibility of using 1,2,4-triazines obtained as photochromic agents was investigated.
- Ivanov,Lichitskii,Dudinov,Martynkin,Krayushkin
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- 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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- Catalytic reactions of dimethyl disulfide with thiophene and benzene
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The gas-phase reaction of dimethyl disulfide with thiophene proceeds under the action of acid catalysts under atmospheric pressure at 160-350°C and a residence time of τ = 0.6-21 s to form thioalkylation and alkylation products. Dimethyl disulfide reacts with benzene to form only alkylation products. Catalysts containing both strong protic and Lewis acid sites, as well as basic sites of moderate strength, are the most active ones.
- Mashkina,Khairulina
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- Reaction of dimethyl disulfide with thiophene catalyzed by zeolite
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Reaction of dimethyl disulfide with thiophene under the action of highly siliceous zeolite at 180-350°C and contact time 0.6-14 s resulted in formation of thioalkylation products, 2-(methylsulfanyl)- and 2,5-bis(methylsulfanyl)thiophenes and also alkylate
- Mashkina,Khairulina
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p. 217 - 220
(2015/04/14)
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- Electrochromic properties of novel chalcones containing triphenylamine moiety
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A series of novel electrochromic chalcones containing triphenylamine units were synthesized by Aldol reaction and characterized by NMR, IR and MS. Their optical, electrochemical properties were investigated using UV-vis, photoluminescence spectra and cyclic voltammetry. The molecular orbital energy levels and excitation energies were calculated by quantum chemical calculation. It was found that the fluorescence intensity is decreasing with formation of charge-transfer state. The existence of electron donating group on triphenylamine unites caused a significant bathochromic shift of the UV absorption maximum and increased EHOMO and ELUMO. The electrochromic property of the synthesized compounds was studied by spectroelectrochemical experiments. The results showed that the chalcones containing triphenylamine moiety presented good electrochromic stability, with a color change from yellow to blue as applied potentials ranging from 0.0 to 2.8 V. The coloring and bleaching time was in the range of 2.9-4.2 s and 1.7-3.3 s, respectively.
- Jin, Huiyi,Li, Xianggao,Tan, Tingfeng,Wang, Shirong,Xiao, Yin,Tian, Jianhua
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p. 154 - 160
(2014/04/17)
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- Investigation of the aroma-active compounds formed in the maillard reaction between glutathione and reducing sugars
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Aroma-active compounds formed during the thermal reaction between glutathione (GSH) and reducing sugars were analyzed by gas chromatography-mass spectrometry (GC-MS) and GC-olfactometry (GC-O) with aroma extract dilution analysis (AEDA). Application of AEDA to glutathione Maillard reaction products (GSH MRPs) led to the identification of 19 aroma-active compounds in the thermal reaction of glutathione with glucose or fructose. In addition, the carbohydrate module labeling (CAMOLA) approach was also employed to elucidate the formation pathways for selected target sulfur aroma compounds, such as 5-methylthiophene-2-carbaldehyde and 3-methylthiophene-2-carbaldehyde, which have not been reported previously. The intact carbon skeleton of glucose via 3-deoxyhexosone is incorporated into 5-methylthiophene-2-carbaldehyde with the hydrogen sulfide of GSH. On the other hand, the formation of 3-methylthiophene2-carbaldehyde may occur via the recombination of a C-4 sugar fragment and mercaptoacetaldehyde.
- Lee, Sang Mi,Jo, Ye-Jin,Kim, Young-Suk
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experimental part
p. 3116 - 3124
(2011/08/05)
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- Carbon-sulfur bond cleavage of methyl-substituted thiophenes with iridium(III)
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Reaction of [Cp*IrHCl]2 (Cp* = η5- C5Me5) with 2-methylthiophene and 2,5-dimethylthiophene at 120 °C in the presence of H2 results in the cleavage of the thiophene carbon-sulfur bond(s). In both cases
- Grochowski, Matthew R.,Brennessel, William W.,Jones, William D.
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p. 2661 - 2667
(2009/09/26)
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- Sulfamic acid as efficient and reusable catalytic system for the synthesis of pyrrole, furan, and thiophene derivatives
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Sulfamic acid has been utilized for the first time as an efficient and reusable catalytic system for the synthesis of heteroaromatics such as pyrrole, furan, and thiophene derivatives from 1,4-diketones. This new procedure offers significant improvements in the reaction rates and yields in a shorter reaction time and a lower reaction temperature contrasted with the reported results. The recovered catalyst can be reused for subsequent runs with only a gradual decrease in activity. The most important feature is that the reaction process is homogeneous whereas the separation process is heterogeneous, which is often seen in other catalysts, and so it is a good character for technical application.
- Luo, Haitang,Kang, Yuru,Li, Qi,Yang, Liming
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p. 144 - 148
(2008/09/18)
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- STUDY OF THE MECHANISM OF RECYCLIZATION OF FURANS INTO THIOPHENES AND SELENOPHENES IN CONDITIONS OF ACID CATALYSIS. 4. STUDY OF THE EFFECT OF THE SOLVENT AND DIRECTION OF REACTIONS OF HYDROLYSIS AND RECYCLIZATION OF 2,5-DIMETHYLFURAN
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The kinetics of hydrolysis of 2,5-dimethylfuran and its recyclization into the corresponding thiophene were investigated in water-alcohol medium in 95, 80, and 50percent ethyl alcohol in the presence of HCl.It was found that the rates of these reactions are a function of both the initial concentration of the acid component and the concentration of water in the alcohol.The rate of hydrolysis is a function of the dilution of the alcohol to a greater degree than the rate of recyclization.
- Gubina, T. I.,Labunskaya, V. I.,Kornienko, G. K.,Borodina, L. A.,Kharchenko, V. G.
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p. 548 - 552
(2007/10/03)
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- Side-chain Effects on the Fragmentation Behaviour of Alkylthiophenes
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The processes leading to the fragment ions formed from alkylthiophene molecule ions by benzylic cleavage without and with transfer of one hydrogen from the side-chain to the ring and the influence of additional methyl groups on the relative importance of these two fragmentation reactions were investigated.
- Lange, D.,Budzikiewicz, H.
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p. 432 - 438
(2007/10/02)
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- INVESTIGATION OF THE MECHANISM OF THE RECYCLIZATION OF FURANS TO THIOPHENES AND SELENOPHENES UNDER ACID-CATALYSIS CONDITIONS. 3. INVESTIGATION OF THE RECYCLIZATION OF HOMOLOGS AND FUNCTIONAL DERIVATIVES OF FURAN. QUANTUM-CHEMICAL CALCULATIONS OF THE OBJECTS OF THE RECYCLIZATION
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The kinetics of the conversion of di-, tri-, and tetraalkylfurans to the corresponding thiophenes were investigated.A correlation between the reactivities and structures of the investigated furans was established.Quantum-chemical calculations of the objects of the recyclization were made.The calculated and experimental data on the reactivities of the investigated compounds were compared.The most likely pathway of the protonation of furans in their recyclization was determined on the basis of calculations of the total energies of the protonated forms.
- Gubina, T. I.,Labunskaya, V. I.,Pankratov, A. N.,Trushin, S. A.,Kharchenko, V. G.
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p. 1393 - 1398
(2007/10/02)
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- Insertion of rhodium into the carbon-sulfur bond of thiophene. Mechanism of a model for the hydrodesulfurization reaction
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The reaction of (C5Me5)Rh(PMe3)(Ph)H with thiophene leads to the elimination of benzene and oxidative addition of the thiophene C-S bond across the Rh(I) center, giving (C5Me5)Rh(PMe3)(SCH=CHCH=CH). Similar reactions occur with 2-methylthiophene, 3-methylthiophene, 2,5-dimethylthiophene, benzothiophene, and dibenzothiophene. Selectivity studies performed with these complexes are consistent with the coordination of sulfur to rhodium prior to C-S bond cleavage. Reversible reductive elimination of thiophene occurs at ～80°C. The diene portion of the C-S insertion ligand undergoes a Diels-Alder reaction with dimethyl acetylenedicarboxylate to give dimethyl phthalate as a major product. The dimethylthiophene complex (C5Me5)Rh(PMe3)(SCMe=CHCH=CMe) was structurally characterized, crystallizing in the monoclinic space group P1 with a = 8.707 (8) A?, b = 14.157 (15) A?, c = 8.637 (5) A?, α = 100.90 (8)°, β = 106.07 (6)°, γ = 87.85 (8)°, V = 1004 (3) A?3, and Z = 2.
- Jones, William D.,Dong, Lingzhen
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p. 559 - 564
(2007/10/02)
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- Gas-phase heteroaromatic substitution. 14. Attack of dimethylfluoronium ion on 2- and 3-methyl-pyrroles, -furans, -and thiophenes
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The gas-phase methylation of 2- and 3-methyl-pyrroles (2P and 3P), -furans (2F and 3F), and thiophenes (2T and 3T) by (CH3)2F+ ions, from γ-radiolysis of CH3F, has been investigated at pressures ranging from 50 to 760 Torr, in the presence of a thermal radical scavenger (O2) and variable concentrations of an added base (NMe3: 0-10 Torr).The mechanism of the methylation process is discussed and the intrinsic positional selectivity of the (CH3)2F+ ions evaluated in the framework of the Charge and Frontier Orbital Control concept.Owing to the very large energy gap between the LUMO of (CH3)2F+ and the HOMOs of the selected heteroaromatic substrates, their gas-phase methylation is characterized by a distinct affinity of the ionic electrophile toward those substrates positions with the highest net negative charge, i.e., the C3 in 2P (100percent), the C4 in 3P (100percent), the heteroatom of 2F and 3F (>80percent), the C5 of 2T (32percent), and the C2 of 3T (47percent).Analysis of the methylated product distribution from 2F and 3F as a function of the experimental conditions reveals that the interaction of the (CH3)2F+ with the heteroatom of furans gives rise to the reversible formation of two sets of electrostatic adducts, i.e., a "chelate" adduct (III) and a single proton-bonded adduct (IV), the first rapidly evolving to the α-substituted heteroarenium intermediate by proximity effects and the latter slowly rearranging to the chelate structure III.Formation of these categories of electrostatic adducts from furans, which is much less extensive in the case of thiophenes and absent in pyrroles, accounts for the apparent pronounced affinity of gaseous alkylating electrophiles, irrespective of their LUMO energy, for the α carbons of furans. Key words: gas-phase ion chemistry, electrophilic aromatic substitution, radiolysis, dimethylfluoronium ions, methylated heteroarenes.
- Cecchi, Patrizio,Pizzabiocca, Adriano,Renzi, Gabriele,Sparapani, Cinzia,Speranza, Maurizio
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p. 2094 - 2103
(2007/10/02)
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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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- MECHANISM OF RECYCLIZATION OF FURANS TO THIOPHENES AND SELENOPHENES UNDER ACID CATALYSIS. 1. KINETIC STUDIES OF THE REACTION OF 2,5-DIALKYLFURANS WITH HYDROGEN SULFIDE IN THE PRESENCE OF HYDROCHLORID ACID
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The transformation of 2,5-dialkylfurans to thiophene by reaction with hydrogen sulfide in the presence of hydrochloric acid was studied.The reaction was found to be first order with respect to the furan; the rate of consumption of the furan did not change with the increasing length of one of the alkyl substituents.Recrystalization in the presence of acid proceeds in two independent directions: through the formation of an intermediate dicarbonyl compound, and by direct conversion of the furan to a thiophene.Kinetic data showed that the reaction occurs mainly by the second route.
- Voronin, S. P.,Gubina, T. I.,Markushina, I. A.,Kharchenko, V. G.
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p. 1113 - 1117
(2007/10/02)
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- Equilibrium studies of thiophene exchange in (η-thiophene)Ru(η-C5H5)+: A model for thiophene adsorption on hydrodesulfurization catalysts
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Equilibrium constants (K′) for the displacement of the π- (i.e., η5-) thiophene (T) ligand in CpRu(T)+ by methyl-substituted thiophenes (Th′), CpRu(T)+ + Th′ ? CpRu(Th′)+ + T, increase as the number of methyl groups in Th′ increases: T (1) 2T (35) 2T (50) 3T(200) 3T (300) 4T (1300). The K′ values increase by a factor of approximately 6 for each methyl in the thiophene (Th′). That thiophenes also adsorb to a Co-Mo/Al2O3 hydrodesulfurization (HDS) catalyst more strongly as the number of methyl groups in the thiophene increases suggests that they are also π-bonded to the catalyst surface. The results suggest that trends in rates of deuterium exchange and hydrodesulfurization on HDS catalysts for a series of methyl-substituted thiophenes are determined by their relative strengths of adsorption to the catalyst surface.
- Hachgenci,Angelici
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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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- STABLE HETEROARENIUM IONS - VIII SOME TRANSFORMATIONS OF ALKYLTHIOPHENIUM IONS AND NEW SYNTHESIS OF 2-t-BUTYLTHIOPHENE
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The ratio of isomeric ?-complexes formed from thiophene, t-butyl chloride and AlCl3 was found to be changed while keeping at room temperature whitin 1-2 days.This allows to obtain after deprotonation 2-t-butylthiophene containing only 3percent of 3-isomer.Transformations of ?-complexes formed by protonation of individual 2- and 3-t-butylthiophenes in the presence of AlCl3 have been studied and there was found that isomerization and deprotonation took place during their storage resulting in mixtures of 2- and 3-t-butylthiophenes (the ratio 97:3) which contained considerable quantities of 2,4-di-t-butylthiophene.Deprotonation of t-butylthiophenium ions in the presence of acetone leads to the formation of respective t-butylsubstituted dimethyldithienylmethanes.
- Belen'kii, L. I.,Yakubov, A. P.
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p. 2471 - 2477
(2007/10/02)
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- Reactions of Thiophene and Alkylthiophenes in Glow Discharge
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The glow discharge reaction of thiophene is shown to produce thioketene and carbon monosulfide along with other gaseous products.The dominant liquid product is ethynylthiophene.Methylthiophenes and especially dimethylthiophenes produce benzene as one of the major liquid products.
- Skramstad, Jan,Chaudhry, Mohammed Shoaib,Garvang, Arne
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p. 509 - 512
(2007/10/02)
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- A NEW REACTION IN COMPOUNDS OF THE FURAN SERIES
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2,5-Dialkylfurans and alcohols, ketones, and esters of the furan series react with hydrogen sulfide under the conditions of acid catalysis and are converted into the corresponding analogs of the thiophene series.A possible reaction mechanism is discussed.
- Kharchenko, V. G.,Gubina, T. I.,Markushina, I. A.
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p. 343 - 347
(2007/10/02)
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