Showing papers on "Tetrahydrofuran published in 2015"
TL;DR: In this article, the Pd catalyst exhibited excellent decarbonylation activity forming furan with 85% yield and the Pt catalyst was reusable even in the absence of external hydrogen.
291 citations
TL;DR: In this paper, an approach to produce levoglucosenone (LGO) from cellulose in yields up to 51% under mild reaction conditions (170-230 °C; 5-20 mM H2SO4) using polar, aprotic solvents such as tetrahydrofuran (THF).
Abstract: Herein, we report an approach to produce levoglucosenone (LGO) from cellulose in yields up to 51% under mild reaction conditions (170–230 °C; 5–20 mM H2SO4) using polar, aprotic solvents such as tetrahydrofuran (THF). LGO can be used to make a wide variety of chemicals from biomass. The water content and solvent used in the reaction system control the product distribution. LGO is produced from the dehydration of levoglucosan (LGA). LGA is produced from cellulose depolymerization. Increasing the water content leads to the production of 5-hydroxymethyl furfural (HMF), obtaining a maximum HMF yield of 30%.
162 citations
TL;DR: In this article, the structural properties of H-ZSM-5, in conjunction with increased reaction performance using the polar aprotic solvent THF, are used for furfuryl alcohol hydrolysis to levulinic acid.
Abstract: Furfuryl alcohol in high concentrations (1 M) was hydrolyzed to levulinic acid in high yields (>70%) using H-ZSM-5 zeolite as the catalyst in monophasic tetrahydrofuran (THF)–water solvent systems. Reaction kinetics studies using H-ZSM-5 were carried out, and combined with results obtained for other Bronsted acid catalysts, we suggest that the structural properties of H-ZSM-5, in conjunction with increased reaction performance using the polar aprotic solvent THF, are effective for furfuryl alcohol hydrolysis to levulinic acid while inhibiting furfuryl alcohol polymerization reactions. In addition, on the basis of results obtained for a wide range of THF–H2O solvent systems (19:1–1:2 w/w), we suggest that the hydrophobic nature of H-ZSM-5 alters the internal solvent microenvironment within the zeolite framework, allowing for high levulinic acid yields, even at low THF solvent concentrations (e.g., 1:2 THF–H2O w/w).
107 citations
TL;DR: A significant kinetic isotope effect (KIE) was recorded, which helps shed light on the mechanistic course.
89 citations
TL;DR: A metal-free cross-dehydrogenative coupling method for the synthesis of N-substituted azoles has been developed and successfully coupling with various ethers and thioethers such as tetrahydrofuran, Tetrahydropyran, 1,4-dioxane, diethyl ether, tetahydrothiophene, and 1,3-dithiolane is developed.
Abstract: A metal-free cross-dehydrogenative coupling method for the synthesis of N-substituted azoles has been developed. The TBAI/TBHP system catalyzed the coupling of azoles with ethers and thioethers via α-C(sp3)–H activation. Under the optimized conditions, a diverse range of un/substituted azoles such as 1H-benzimidazole, 9H-purine, 1H-benzotriazole, 1H-1,2,3-triazole, 1H-1,2,4-triazole, and 1H-pyrazole were successfully employed for coupling with various ethers and thioethers such as tetrahydrofuran, tetrahydropyran, 1,4-dioxane, diethyl ether, tetrahydrothiophene, and 1,3-dithiolane.
63 citations
TL;DR: An auxiliary-enabled Pd-catalyzed highly regio- and stereoselective sp(3) C-H activation and the direct arylation of the C3-position of oxygen heterocycles, such as tetrahydrofuran and 1,4-benzodioxane systems, are reported.
Abstract: An auxiliary-enabled Pd-catalyzed highly regio- and stereoselective sp3 C–H activation and the direct arylation of the C3-position of oxygen heterocycles, such as tetrahydrofuran and 1,4-benzodioxane systems, are reported. An efficient stereoselective construction of cis 2,3-disubstituted tetrahydrofuran derivatives (analogues of norlignans) and cis 2,3-disubstituted 1,4-benzodioxane derivatives (analogues of neolignans) is described. The direct C(sp3)–H arylation of the C3-position of (R)- or (S)- tetrahydrofuran-2-carboxamides furnished the corresponding (2R,3R) and (2S,3S) C3-arylated THF scaffolds as major compounds with very high regio- and diastereoselectivities. The stereochemistry of the products obtained in this work were unambiguously assigned on the basis of the X-ray structure analyses of representative compounds 3b, 3e, 4p, and 7.
62 citations
TL;DR: In this article, acid-catalyzed conversions of three typical C6 sugar monomers/oligomers (glucose, maltose, and beta-cyclodextrins) to levulinic acid in water, tetrahydrofuran (THF) and toluene have been investigated over a solid acid catalyst Amberlyst 70 (A70), aiming to understand behaviors of the sugars in the solvents with distinct polarities.
61 citations
TL;DR: In this paper, a new carbon paste electrode was described, which contains the room temperature ionic liquid tri(tert-butyl)(dodecyl)phosphonium tetrafluoroborate as binder.
Abstract: A new carbon paste electrode is described, which contains the room temperature ionic liquid (RTIL) tri(tert-butyl)(dodecyl)phosphonium tetrafluoroborate as binder. The advantages of this electrode are a high conductivity, very wide electrochemical window (5.6 V from 2.7 to −2.9 V, one of the widest ever reported for RTILs), stability in time, and reproducibility. This RTIL-carbon paste electrode (CPE) allows determining the current-voltage characteristics of redox-active compounds. Thus, the newly synthesized insoluble compound poly-tris(μ2-1,1′-ferrocenediyl-phenylhydrophosphinato-phenylphosphinato)-iron(III) tetrahydrofuran solvate {μ2-[FeII(η5-C5H4–P(PhOO)(η5-C5H4–P(PhOOH))]3FeIII}·THF was studied, and a quasi-reversible three-electron oxidation could be observed at a potential more positive than that of ferrocene. A comparison of voltammograms on the paraffin-CPE and on the novel RTIL-CPE shows the advantages of the latter.
59 citations
TL;DR: In this paper, a novel heterogeneous palladium copper bimetallic catalyst supported on zirconia was synthesized and fully characterized for one-pot synthesis of γ-valerolactone, 1,4-pentanediol, and 2-methyl tetrahydrofuran using water as a solvent.
Abstract: Synthesis of chemicals derived from biomass using heterogeneous catalysts with water as a solvent elegantly fits into the realm of sustainable chemistry. In this work, a novel heterogeneous palladium copper bimetallic catalyst supported on zirconia was synthesized and fully characterized. This catalyst was used in one-pot synthesis of γ-valerolactone, 1,4-pentanediol, and 2-methyl tetrahydrofuran from levulinic acid and hydrogen using water as a solvent. The catalyst consists of 1% palladium and 29% copper supported on zirconia and is characterized per se and after reuse by using elemental analysis, FTIR, NH3-TPD, XRD, and BET surface area, XPS, SEM, and TEM analysis. This is the first ever report on the direct synthesis of 1,4-pentanediol and 2-methyl tetrahydrofuran using water as a solvent. Reaction mechanism and kinetic modeling was done to validate the experimental results. The results reported are thus a combination of synthesis of a novel catalyst with its full characterization, its application in ...
58 citations
TL;DR: An azobenzene-containing zirconium metal-organic framework was demonstrated to be an effective heterogeneous catalyst for the direct amidation of benzoic acids in tetrahydrofuran at 70 °C.
53 citations
TL;DR: In the presence of the di-tert-butyl peroxide oxidant, cyclic ethers such as tetrahydrofuran, 1,4-dioxane, and tetrahYDropyran successfully undergo C-H/N-H cross dehydrogenative coupling (CDC) with various carbazole or indole derivatives in good-to-excellent yields.
Abstract: A simple α-C–H amination of cyclic ether with indole/carbazole derivatives has been accomplished by employing copper(II) chloride/bipy as the catalyst system. In the presence of the di-tert-butyl peroxide oxidant, cyclic ethers such as tetrahydrofuran, 1,4-dioxane, and tetrahydropyran successfully undergo C–H/N–H cross dehydrogenative coupling (CDC) with various carbazole or indole derivatives in good-to-excellent yields.
TL;DR: In this article, the preparation of crosslinked membranes with a zwitterionic structure based on a facile reaction between a newly synthesized copolyazole with free OH groups and 3-glycidyloxypropyl)trimethoxysilane (GPTMS) is reported.
TL;DR: The model applies to investigate the separation of toluene (TO), nortriptyline (NT), cytosine (CYT), and niacin (NA) on an organic ethyl/inorganic silica hybrid adsorbent reveals the relative importance of adsorption and partitioning mechanisms depends in a complex way from analyte properties and experimental parameters and cannot be predicted generally.
TL;DR: In this paper, the experimental data for the phase equilibrium of methane (CH 4 ) hydrate system have been obtained in the presence of tetrahydrofuran (THF) and tetra- n -butyl ammonium bromide (TBAB) with various inhibitors.
TL;DR: A systematic investigation was conducted to explore how different concentrations of structure-directing agents affected the frameworks of resultant metal-organic frameworks and showed that the catalytic activity of 2 was much higher than that of 1 and 3, because of its unique structural features, including accessible catalytic sites and suitable channel size and shape.
Abstract: Solvent templates induced Co-based metal–organic materials; conformational isomers {[Co2(pdpa)(CH3CN)(H2O)3]·CH3OH·H2O}n (1) and {[Co2(pdpa)(CH3CN)(H2O)3]}n (2) and {[Co5(pdpa)2(μ3-OH)2(H2O)6]·2H2O}n (3) [H4pdpa = 5,5′-(pentane-1,2-diyl)-bis(oxy)diisophthalic acid] were synthesized under the same solvothermal conditions except with different concentrations of cyclic ethers (1,4-dioxane or tetrahydrofuran) as structure-directing agents. Structural transformations from a three-dimensional (3D) framework of 1 containing channels with dimensions of ∼6 A × 6 A to a two-dimensional layer structure of 2 consisting of large open channels with a size of ∼15 A × 8 A and then to a 3D nonporous framework of 3, resulting from the different concentrations of cyclic ethers, were observed. The anion−π interactions between electron-efficient oxygen atoms of cyclic ethers and electron-deficient dicarboxylic acid aromatic cores in H4pdpa imported into the synthetic process accounted for the conformational change of the liga...
TL;DR: It is shown that low concentrations of water in the THF solvent significantly alter reaction rates and selectivities for the formation of reaction products by hydrogenation and hydrogenolysis processes.
Abstract: Reaction kinetics were studied to quantify the effects of water on the conversion of hydroxymethylfurfural (HMF) in THF over Cu/γ-Al2 O3 at 448 K using molecular H2 as the hydrogen source. We show that low concentrations of water (5 wt %) in the THF solvent significantly alter reaction rates and selectivities for the formation of reaction products by hydrogenation and hydrogenolysis processes. In the absence of water, HMF was converted primarily to hydrogenolysis products 2-methyl-5-hydroxymethylfuran (MHMF) and 2,5-dimethylfuran (DMF), whereas reactions carried out in THF-H2 O mixtures (THF/H2 O=95:5 w/w) led to the selective production of the hydrogenation product 2,5-bis(hydroxymethyl)furan (BHMF) and inhibition of HMF hydrogenolysis.
TL;DR: The solvent dependent properties of polyethyleneimine (PEI)-capped Cu nanoclusters are discussed in this article, where the PEI-encapsulated Cu nanclusters were dispersed in 12 polar organic solvents, and in water and alcohols, the nanocluster display similar properties and could be stable in the dark.
Abstract: The solvent-dependent properties of polyethyleneimine (PEI)-capped Cu nanoclusters are discussed in this study. The PEI-encapsulated Cu nanoclusters were dispersed in 12 polar organic solvents, and in water and alcohols, the nanoclusters display similar properties and could be stable in the dark. Moreover, Cu nanoclusters exhibit a blue shift of the emission peak in tetrahydrofuran (THF) and 1,4-dioxane, and the absorption spectra change dramatically. Furthermore, in THF the fluorescence intensity increases significantly over time. Besides, the absorption spectra also display a significant change in acetonitrile, dimethyl sulfoxide, and ethylene glycol monomethyl ether, while the emission bands show no obvious shift. In acetonitrile, THF, and 1,4-dioxane, the solvents look milky under bright light, and the fluorescence colors look more blue under a UV lamp. The solvent effect on the fluorescence and absorption spectra of the PEI-capped Cu nanoclusters in water–THF mixtures at different solvent ratios is d...
TL;DR: Direct follow-up reactions allow the preparation of MoS2, FeAs2, or Re4Mo nanoparticles of similar size as the pristine metals (≤10 nm).
Abstract: Mo(0), W(0), Fe(0), Ru(0), Re(0), and Zn(0) nanoparticles—essentially base metals—are prepared as a general strategy by a sodium naphthalenide ([NaNaph])-driven reduction of simple metal chlorides in ethers (1,2-dimethoxyethane (DME), tetrahydrofuran (THF)). All the nanoparticles have diameters ≤10 nm, and they can be obtained either as powder samples or long-term stable suspensions. Direct follow-up reactions (e.g., Mo(0)+S8, FeCl3+AsCl3, ReCl5+MoCl5), moreover, allow the preparation of MoS2, FeAs2, or Re4Mo nanoparticles of similar size as the pristine metals (≤10 nm).
TL;DR: NMR spectroscopy and deuterium labeling experiments confirmed the selective cleavage of dihydrogen by the highly polar Ca-Si bond in 1.
Abstract: Protonolysis of bis(triphenylsilyl)calcium [Ca(SiPh3)2(THF)4] (1; THF = tetrahydrofuran) with the NNNN-type macrocyclic amido triamine (Me3TACD)H (TACD = 1,4,7-triazacyclododecane) gave the heteroleptic calcium complex [Ca(Me3TACD)SiPh3] (2) in quantitative yield. Hydrogenolysis of 2 gave the cationic tricalcium dihydride cluster [Ca3H2(Me3TACD)3]+(SiPh3)−·2THF (4a) in high yield with concomitant formation of HSiPh3. In the crystal, 4a consists of a cluster cation and a free triphenylsilyl anion. 1H NMR spectroscopy and deuterium labeling experiments confirmed the selective cleavage of dihydrogen by the highly polar Ca–Si bond in 1.
TL;DR: In this paper, the authors evaluated the effect of DTAC and Tween-20 (Polysorbate 20) surfactants on mixed hydrogen/tetrahydrofuran (THF) hydrate formation.
TL;DR: In this paper, the phase equilibrium of (CO2+N2) binary guest-mixtures was investigated using isochoric multi-step heating dissociation method in various systems, i.e., pure water, Tetrahydrofuran (THF, yTHF = ǫ 0.004, 0.012,0.042 m fraction) aqueous solution, natural seawater, seasand, and (seawater+seasand) mixture.
TL;DR: In this article, a comparison between tetrahydrofuran (THF) and 1,3 dioxolane (DIOX) in terms of their respective performances as promoters for the formation of clathrate hydrates with CO2 was made.
TL;DR: A picture is generated in which water mediates between THF pairs--mediation that affects vibrational frequencies of both species, and water's hydrogen-bonded resonance gains oscillator strength due to its mediating configuration.
Abstract: Tetrahydrofuran (THF) is well-known as a clathrate former as well as a promoter for gas hydrate formation. This work examines interactions between water and tetrahydrofuran via the effect on water’s vibrational spectrum. Due to water’s large oscillator strength in the hydrogen-bonded region, interactions are diagnosed by isolating small clusters in a transparent medium (carbon tetrachloride in this study). A weak THF/water hydrogen bond is reflected by a 3450 cm–1 OH-donor vibration (blue shifted from the water/water hydrogen bond) and a 3685 cm–1 nonbonded OH stretch (blue shifted 22 cm–1 from the decoupled OH stretch in this medium). Increasing the THF concentration results in another 20 cm–1 blue shift of the OH-donor stretch. Additional THF does not complex with free water but rather joins with existing THF/water structures to form a cluster enriched in THF. These results complement previous work examining THF vibrations in clathrate hydrates. Together, they generate a picture in which water mediates ...
TL;DR: In this article, the authors performed molecular dynamics simulations of the ammonia and methanol-based clathrate hydrates with the emphasis on characterizing hydrogen-bonding interactions of these guest molecules with the water lattice.
Abstract: We performed molecular dynamics simulations of the ammonia and methanol-based clathrate hydrates with the emphasis on characterizing hydrogen-bonding interactions of these guest molecules with the water lattice. Systems studied include structure II (sII) binary clathrate hydrates of tetrahydrofuran (THF) (large cage, L) + NH3 (small cage, S) and THF (L) + CH3OH (S), the structure I (sI) pure NH3 (L), pure CH3OH (L), the binary NH3 (L) + CH4 (S), and binary CH3OH (L) + CH4 (S) clathrate hydrates. We simulated these clathrate hydrates with the transferable intermolecular potential with four point changes (TIP4P) water potential and the TIP4P/ice water potential to determine the effect of the water potential on the predicted hydrogen bonding of the guest molecules. Simulations show that, despite strongly hydrogen bonding with the framework water molecules, clathrate hydrate phases with NH3 and CH3OH can be stable within temperatures ranges up to 240 K. Indeed, a limited number of thermodynamic integration fr...
TL;DR: In this article, the authors studied the equilibrium behavior of organolead trihalide perovskites in aqueous solution of CH3NH3PbI3 single crystals (MSCs).
Abstract: Crystallization and decomposition of organolead trihalide perovskites (OTPs) are very sensitive to the presence of water in precursor or in ambient conditions. Thus, understanding equilibrium behaviours (crystallization and decomposition) of OTPs in aqueous solution is very critical for OTP solar cells fabricated with water-based precursor solutions. Here, equilibrium behaviours in an aqueous solution of CH3NH3PbI3 (MAPbI3) single crystals (MSCs) were studied. Diethyl ether, as an antisolvent, effectively diffused and induced MSC growth by screening different solvents (diethyl ether, tetrahydrofuran, dichloromethane, and chloroform). The structure transforms from the initial PbI2 to intermediate (HxPbI2+x·xH2O) and finally MSCs were observed by X-ray diffraction. Decomposition of MSCs in aqueous solution was significantly enhanced by potassium iodide coordination and inhibited by CH3NH3I (MAI) addition. We ascribed this inhibition behaviour to suppressing MAI migration from the MSC crystal structure. Finally, the optical properties of MSC were studied.
TL;DR: In this paper, the stability limit and kinetic properties of THF hydrates were simulated using molecular dynamics (MD) simulations, and the change in dissociation temperature with pressure and concentration of threedrofuran in the aqueous phase were well reproduced with MD simulations.
Abstract: Tetrahydrofuran (THF) is an effective promoter of methane hydrates, and itself with water can form clathrate hydrates even without the presence of methane gas. In this work, the stability limit and kinetic properties of THF hydrates were simulated using molecular dynamics (MD) simulations. The change in dissociation temperature of THF hydrates with pressure and concentration of THF in the aqueous phase were well reproduced with MD simulations. The rate of growth of THF hydrates is found to exhibit a maximum value when the liquid-phase THF concentration is about 0.3–0.8 times (depending on temperature) of the THF concentration in the hydrate phase. The existence of some optimal growth concentration explains the preferred lateral growth in experiments. The maximum growth rate is a result of two competing effects: the adsorption of THF molecules to the growing interface, which is the limiting step at low THF concentrations, and the desorption/rearrangement of THF molecules at the interface, limiting step at ...
TL;DR: The adsorption of diethyl ether (Et2O) on Si(001) was studied by means of scanning tunneling microscopy (STM) and photoelectron spectroscopy as mentioned in this paper.
Abstract: The adsorption of diethyl ether (Et2O) on Si(001) was studied by means of scanning tunneling microscopy (STM) and photoelectron spectroscopy. Et2O reacts on Si(001) via a datively bonded intermediate, which was isolated at surface temperatures below 100 K. At higher surface temperature, Et2O converts dissociatively into the final state by cleaving one O−C bond; the resulting −O−C2H5 and −C2H5 fragments are found to attach on two Si dimers of neighboring dimer rows. Tip- induced hopping of the −C2H5 fragment on one dimer was observed at positive sample bias. The results are discussed in the context of recent experiments on the reaction of tetrahydrofuran (THF) on Si(001) (Mette et al. ChemPhysChem 2014, 15, 3725) and allow a more general description of the reaction of ethers on Si(001).
TL;DR: A nickel- and manganese-catalyzed decarboxylative cross coupling of α, β-unsaturated carboxylic acids with cyclic ethers such as tetrahydrofuran and 1, 4-dioxane was developed and achieved Oxyalkylation.
Abstract: A nickel- and manganese-catalyzed decarboxylative cross coupling of α, β-unsaturated carboxylic acids with cyclic ethers such as tetrahydrofuran and 1, 4-dioxane was developed. Oxyalkylation was achieved when nickel acetate was used as catalyst, while manganese acetate promoted the reaction of alkenylation.
TL;DR: Poly(3-hexylthiophene) (P3HT) is investigated and it is found that polymerization of 1 with 2 in H2 O/THF affords P3HT with a narrower molecular weight distribution and controlled tolyl/H ends, as compared to the reaction in dry THF.
Abstract: Although water promotes Suzuki-Miyaura coupling reaction, it also induces side reactions such as deboronation and dehalogenation. Therefore, Suzuki-Miyaura polymerization of triolborate halothiophene monomer 1 with (t) Bu3 PPd(o-tolyl)Br (2) in dry tetrahydrofuran (THF) is investigated. However, the resultant poly(3-hexylthiophene) (P3HT) shows a broad molecular weight distribution and uncontrolled polymer ends. Model reactions of a number of boron reagents 3 with 2,5-dibromothiophene (4) in the presence or absence of water indicate that intramolecular transfer of the catalyst is hardly affected by the boron moiety of 3, whereas it is hindered in the absence of water. Indeed, polymerization of 1 with 2 in H2 O/THF affords P3HT with a narrower molecular weight distribution and controlled tolyl/H ends, as compared to the reaction in dry THF.
TL;DR: The synthesis of three new dizinc(II) complexes bearing a macrocyclic [2 + 2] Schiff base ligand is reported, with good control, as evidenced by the linear fit to a plot of molecular weight versus conversion, the narrow dispersities, and the limited transesterification.
Abstract: The synthesis of three new dizinc(II) complexes bearing a macrocyclic [2 + 2] Schiff base ligand is reported. The bis(anilido)tetraimine macrocycle reacts with diethylzinc to form a bis(ethyl)dizinc(II) complex, [LEtZn2Et2] (1). The reaction of complex 1 with isopropyl alcohol is reported, forming a bis(isopropyl alkoxide)dizinc complex, [LEtZn2(iPrO)2] (2). Furthermore, complex 1, with 2 equiv of alcohol, is applied as an initiator for racemic lactide ring-opening polymerization. It shows moderately high activity, resulting in a pseudo-first-order rate coefficient of 9.8 × 10–3 min–1, with [LA] = 1 M and [initiator] = 5 mM at 25 °C and in a tetrahydrofuran solvent. Polymerization occurs with good control, as evidenced by the linear fit to a plot of molecular weight versus conversion, the narrow dispersities, and the limited transesterification. The same initiating system is inactive for the ring-opening copolymerization of carbon dioxide (CO2) and cyclohexene oxide at 80 °C and 1 bar of CO2 pressure. How...