Showing papers on "Tetrahydrofuran published in 2020"

Stable abnormal N-heterocyclic carbenes and their applications.

Abstract: Although N-heterocyclic carbenes (NHCs) have been known as ligands for organometallic complexes since the 1960s, these carbenes did not attract considerable attention until Arduengo et al. reported the isolation of a metal-free imidazol-2-ylidene in 1991. In 2001 Crabtree et al. reported a few complexes featuring an NHC isomer, namely an imidazol-5-ylidene, also termed abnormal NHC (aNHCs). In 2009, it was shown that providing to protect the C-2 position of an imidazolium salt, the deprotonation occurred at the C-5 position, affording imidazol-5-ylidenes that could be isolated. Over the last ten years, stable aNHCs have been used for designing a range of catalysts employing Pd(II), Cu(I), Ni(II), Fe(0), Zn(II), Ag(I), and Au(I/III) metal based precursors. These catalysts were utilized for different organic transformations such as the Suzuki–Miyaura cross-coupling reaction, C–H bond activation, dehydrogenative coupling, Huisgen 1,3-dipolar cycloaddition (click reaction), hydroheteroarylation, hydrosilylation reaction and migratory insertion of carbenes. Main-group metal complexes were also synthesized, including K(I), Al(III), Zn(II), Sn(II), Ge(II), and Si(II/IV). Among them, K(I), Al(III), and Zn(II) complexes were used for the polymerization of caprolactone and rac-lactide at room temperature. In addition, based on the superior nucleophilicity of aNHCs, relative to that of their nNHCs isomers, they were used for small molecules activation, such as carbon dioxide (CO2), nitrous oxide (N2O), tetrahydrofuran (THF), tetrahydrothiophene and 9-borabicyclo[3.3.1]nonane (9BBN). aNHCs have also been shown to be efficient metal-free catalysts for ring opening polymerization of different cyclic esters at room temperature; they are among the most active metal-free catalysts for e-caprolactone polymerization. Recently, aNHCs successfully accomplished the metal-free catalytic formylation of amides using CO2 and the catalytic reduction of carbon dioxide, including atmospheric CO2, into methanol, under ambient conditions. Although other transition metal complexes featuring aNHCs as ligand have been prepared and used in catalysis, this review article summarize the results obtained with the isolated aNHCs.

Mechanistic role of protonated polar additives in ethanol for selective transformation of biomass-related compounds

Abstract: We report on a combined experimental, spectroscopic and theoretical study of acid catalysed dehydration-etherification of fructose in ethanol for understanding the mechanistic role of polar solvent additives and product selectivity. Herein, we show that polar solvent additives (e.g. tetrahydrofuran, acetone, acetonitrile, gamma-valerolactone, dimethyl sulfoxide) protonated with a common solid acid catalyst in ethanol allow transformation of biomass-related compounds into desired dehydration or etherification products. Fructose in ethanol with DMSO additive is selectively transformed into 5-hydroxymethylfurfural with negligible formation of 5-ethoxymethylfurfural due to preferential DMSO protonation according to its polarity. Spectroscopic methods and density functional theory show that additives having higher polarity than ethanol are readily protonated and act as the key catalytic protonation species and as the key stabilization species for reaction intermediates. Understanding the mechanism of protonated polar additives in reaction systems allows one to tailor selectivity in acid-catalyzed dehydration-etherification schemes and to develop sustainable chemistry for biomass resources.

Effect of Mixed-Solvent Environments on the Selectivity of Acid-Catalyzed Dehydration Reactions

Abstract: The composition of the liquid phase can alter the rates of individual reaction steps and thus alter the selectivity of acid-catalyzed reactions, but these solvent effects are difficult to anticipate for design purposes. Herein, we report the kinetics and selectivity of Bronsted acid-catalyzed 1,2-propanediol dehydration in pure water and in aqueous mixtures of the polar aprotic cosolvents γ-valerolactone, 1,4-dioxane, tetrahydrofuran, N-methyl-2-pyrrolidone, tetramethylene sulfoxide, and dimethyl sulfoxide at 433 K. We find that the major product of 1,2-propanediol dehydration is propanal in most mixed-solvent environments with selectivities between 1 and 68 mol %. In contrast, 1,2-propanediol dehydration in aqueous mixtures of dimethyl sulfoxide affords acetone as the major product with up to 48% selectivity with minimal propanal formation. We use classical molecular dynamics simulations to probe these solvent effects by computing the difference between the solvation free energies of 1,2-propanediol and ...

Water acting as a catalyst for electron-driven molecular break-up of tetrahydrofuran

Abstract: Low-energy electron-induced reactions in hydrated molecular complexes are important in various fields ranging from the Earth's environment to radiobiological processes including radiation therapy. Nevertheless, our understanding of the reaction mechanisms in particular in the condensed phase and the role of water in aqueous environments is incomplete. Here we use small hydrogen-bonded pure and mixed dimers of the heterocyclic molecule tetrahydrofuran (THF) and water as models for biochemically relevant systems. For electron-impact-induced ionization of these dimers, a molecular ring-break mechanism is observed, which is absent for the THF monomer. Employing coincident fragment ion mass and electron momentum spectroscopy, and theoretical calculations, we find that ionization of the outermost THF orbital initiates significant rearrangement of the dimer structure increasing the internal energy and leading to THF ring-break. These results demonstrate that the local environment in form of hydrogen-bonded molecules can considerably affect the stability of molecular covalent bonds.

Solubility of Benzanilide Crystals in Organic Solvents

Abstract: The solubility of benzanilide in sixteen pure organic solvents, including N, N-dimethylformamide, tetrahydrofuran, butanone, acetone, ethyl acetate, dichloromethane, n-butanol, diethyl ether, n-pro...

Interfacial Mass Transfer in Water-Toluene Systems

Abstract: In this work the interfacial mass transfer of the system water–toluene with four different transferring components (acetone, ethanol, tetrahydrofuran, and acetonitrile) was examined. For this the l...

Nanocarbon-Immobilized Membranes for Separation of Tetrahydrofuran from Water via Membrane Distillation

Abstract: We present the application of nanocarbon-immobilized membranes for the separation and recovery of tetrahydrofuran (THF) from water via membrane distillation Several nanocarbons, namely carbon nano

Diversity-Oriented Synthesis of N,N,O-Trisubstituted Hydroxylamines from Alcohols and Amines by N–O Bond Formation

Abstract: Magnesium dialkylamides react with alcohol-derived 2-methyl-2-tetrahydropyranyl alkyl peroxides (MTHPs) in tetrahydrofuran at 0 °C to give N,N,O-trisubstituted hydroxylamines suitable for medicinal...

Electrocatalytic Alcohol Oxidation with Iron-Based Acceptorless Alcohol Dehydrogenation Catalyst.

Abstract: Electrochemical and chemical studies reveal that the amido complex (PNHxP)Fe(CO)(H)(X) (FeN 1, x = 0, X = 0; Fe(H)(NH) 2, x = 1, X = H; PNHP = bis[2-(diisopropylphosphino)ethyl]amine) is active for the electrocatalytic oxidation of isopropanol. At room temperature, the amido FeN 1 dehydrogenates isopropanol to form acetone. The resulting amino hydride complex Fe(H)(NH) 2 is subsequently oxidized by one electron at a low potential (-0.74 V versus ferrocene/ferrocenium, Fc0/+) in tetrahydrofuran. In the presence of strong base (phosphazene base P2-Et, Et-N = P2(dma)5, P2), this oxidation process becomes a two-electron, two-proton process that regenerates FeN 1. FeN 1 is active for the electrooxidation of isopropanol in the presence of strong base (i.e., P2) with an onset potential near -1 V versus Fc0/+. By cyclic voltammetry, fast turnover frequencies of 1.7 s-1 for isopropanol oxidation are achieved with FeN 1. Controlled potential electrolysis studies confirm that the product of isopropanol electrooxidation is acetone, generated with high Faradaic efficiency (∼100%).

Catalytic Asymmetric Synthesis of Tetrahydrofuran Spirooxindoles via a Dinuclear Zinc Catalyst

Abstract: An asymmetric Michael/hemiketalization and Fridel-Crafts reaction has been reported through a one-pot reaction. A number of structurally novel tetrahydrofuran spirooxindoles are synthesized in the presence of a 10 mol % dinuclear zinc catalyst with diastereomer ratios (dr) of 3:1-13:1 and an enantiomeric excess (ee) of 75-99%. The reaction can be performed on a gram scale without impacting its efficiency. The absolute configuration of products is confirmed by X-ray single crystal structure analysis, and a possible mechanism is proposed.

Designing highly fluorescent, arylated poly(phenylene vinylene)s of intrinsic microporosity

Abstract: Three new polymers containing tetraphenylethylene and diphenyl-dinaphthylethylene cores and their corresponding monomeric model compounds were synthesized and fully characterized aiming to investigate their photoluminescence efficiency, microporosity and Brunauer–Emmett–Teller-derived surface areas (SBET). Comprehensive photophysical characterization was undertaken in the solid state (powder and thin films), in tetrahydrofuran (THF) solution and in mixtures of “good” and “poor” solvent to induce aggregation (THF:water mixtures). Aggregation induced emission (AIE) was found for the tert-butyl-TPE monomer and polymer and diphenyl-dinaphthylethylene monomer with the increase of the water amount in THF:water mixtures and in the solid state. The tert-butyl substituted TPE derivatives display the highest fluorescence quantum yield (ϕF) values: 0.14 to 0.30 (in powder) and 0.46 to 0.64 in thin films. In contrast, with the diphenyl-dinaphthylethylene (meta and para-phenylene) polymers aggregation caused quenching (ACQ) occurs in THF:water mixtures (ϕF ≤ 0.011) and in the solid state (ϕF ≤ 0.012). The microporosity of the soluble conjugated polymers as potential conjugated polymers of intrinsic microporosity (cPIMs) was further investigated. The SBET of the polymers were related to their optical properties. The polymers show an attractive combination of high SBET surface area (417 m2 g−1) and the occurrence of distinct AIE effects for the tert-butyl-TPE polymer while the diphenyl-dinaphthylethylene polymers do not exhibit microporosity (SBET ≤ 17 m2 g−1) and show ACQ behavior.

Reactivity and stability of ion pairs, dimers and tetramers versus solvent polarity: SNAr fluorination of 2-bromobenzonitrile with tetramethylammonium fluoride

Abstract: Anion–molecule reactions have a substantial solvent effect, which decreases with the solvent polarity. However, less solvation leads to the formation of ion pairs and higher aggregates that are usually less reactive. Consequently, theoretical determination of the best solvent for the reaction needs to consider all the species in equilibrium. In this report, we have investigated the wide range of solvent polarity in the SNAr reaction of the tetramethylammonium fluoride (TMAF) with 2-bromobenzonitrile, as well as the formation of ion pairs, dimers and tetramers using molecular dynamics and density functional calculations with continuum solvation. Five solvents were considered: methanol, dimethylformamide, pyridine, tetrahydrofuran and benzene. The TMAF exists predominantly as free ions in methanol, as ion pairs in dimethylformamide and pyridine, and as tetramers in tetrahydrofuran and benzene. The reaction takes place through free ions in methanol, ion pairs in dimethylformamide, pyridine and tetrahydrofuran, and via dimer in benzene. The calculations suggest that dimethylformamide and pyridine are the best solvents for this reaction.

Flow-OrientedSynthesis of Li2S and Li3PS4·3THF:Opening Up a Completely Solvent-BasedSolid Electrolyte Value Chain

Abstract: Sulfide-based solid electrolytes are considered as the likeliest enabler of all-solid-state batteries. However, Li2Sthe indispensable starting material for their preparationis complicated to synthesize and thus extremely expensive. This work reports an innovative approach to the synthesis of Li2S and its simultaneous linking to the transformation to Li3PS4·3THF in a sequential one-pot reaction. Lithium and sulfur are reacted in tetrahydrofuran (THF) with cheap naphthalene as an electron transfer agent. Mechanistically, naphthalene is reduced by lithium to its corresponding radical anion, which in turn reduces the sulfur species until S2– is reached. Without intermediate workup, P2S5 is added to the reaction vessel to form Li3PS4·3THF. High loadings of naphthalene allow for a quick completion of the first step in <8 h, while they do not hamper the subsequent formation of Li3PS4·3THF. After removing naphthalene, Li3PS4·3THF is utilized to synthesize promising sulfide-based electrolytes, such as β-Li3PS4 or Li6PS5Cl exhibiting typical Li+-ion conductivities of 0.1 and 1.9 mS/cm, respectively. β-Li3PS4 produced this way and β-Li3PS4 synthesized from commercial Li2S do not exhibit any difference in their performance in an all-solid-state battery.

Wet‐Chemical Tuning of Li3−xPS4 (0≤x≤0.3) Enabled by Dual Solvents for All‐Solid‐State Lithium‐Ion Batteries

Abstract: All-solid-state lithium-ion batteries (ASLBs) employing sulfide solid electrolytes are attractive next-generation rechargeable batteries that could offer improved safety and energy density. Recently, wet syntheses or processes for sulfide solid electrolyte materials have opened opportunities to explore new materials and practical fabrication methods for ASLBs. A new wet-chemical route for the synthesis of Li-deficient Li3-x PS4 (0≤x≤0.3) has been developed, which is enabled by dual solvents. Owing to its miscibility with tetrahydrofuran and ability to dissolve elemental sulfur, o-xylene as a cosolvent facilitates the wet-chemical synthesis of Li3-x PS4 . Li3-x PS4 (0≤x≤0.15) derived by using dual solvents shows Li+ conductivity of approximately 0.2 mS cm-1 at 30 °C, in contrast to 0.034 mS cm-1 for a sample obtained by using a conventional single solvent (tetrahydrofuran, x=0.15). The evolution of the structure for Li3-x PS4 is also investigated by complementary analysis using X-ray diffraction, Raman, and X-ray photoelectron spectroscopy measurements. LiCoO2 /Li-In ASLBs employing Li2.85 PS4 obtained by using dual solvents exhibit a reversible capacity of 130 mA h g-1 with good cycle retention at 30 °C, outperforming cells with Li2.85 PS4 obtained by using a conventional single solvent.

Bimetallic Arylamide-Ligated Rare-Earth Metal Complexes: Synthesis, Characterization, and Stereo-Selectively Switchable Property in 2-Vinylpyridine Polymerization.

Abstract: Bimetallic complexes are expected to offer unique catalytic property, by facilitating cooperative effects between proximate functional groups or adjacent active metal centers, and thus have attracted increasing attention in the chemical community. Treatment of Ln(CH2SiMe3)3(THF)2 or Ln(CH2C6H4NMe2-o)3 with 1,4-(C6H5NH)2C6H4 in a 2:1 molar ratio in tetrahydrofuran (THF) generated a series of bimetallic arylamide-ligated rare-earth metal alkyl complexes [1,4-(C6H5N)2C6H4][Ln(CH2SiMe3)2(THF)2]2 (Ln = Sc (1), Lu (2), Y (3)), and aminobenzyl complexes [1,4-(C6H5N)2C6H4][Ln(CH2C6H4NMe2-o)2(THF)x]2 (Ln = Sc (4), x = 0; Lu (5), Y (6), x = 1) in 65-73% isolated yields. To reveal the polymerization difference between bimetallic and monometallic rare-earth metal complexes, the monoarylamide-ligated scandium bis(aminobenzyl) complex [(C6H5)2N]Sc(CH2C6H4NMe2-o)2 (7) was prepared by the reaction of Sc(CH2C6H4NMe2-o)3 with 1 equiv of diphenylamine (C6H5)2NH. All these rare-earth metal complexes were characterized by elemental analysis and NMR spectroscopy. The molecular structures of complexes 4 and 6 were authenticated by single-crystal X-ray diffraction. Complexes 2, 3, 5, and 6 alone were highly active for 2-vinylpyridine (2VP) polymerization at room temperature, giving poly-2VP with good iso-selectivity (mm). After activation with 2 equiv of [Ph3C][B(C6F5)4] or [PhNHMe2][B(C6F5)4], these complexes demonstrated an improved iso-selectivity (mm up to 96%) toward 2VP polymerization compared to their neutral analogues. In comparison, the bimetallic scandium complexes 1 and 4 showed relatively poor activity toward 2VP polymerization under the same conditions. However, the stereoselectivity of the polymerization could be switched from iso-tacticity to syndio-rich selectivity solely by tuning active species from only one scandium precatalyst. The catalyst system of complex 4/[PhNMe2H][B(C6F5)4] was able to promote a controlled syndio-specific polymerization of 2VP. The polymerization was experimentally verified to proceed via group transfer mechanism. Preliminary results indicated that the bimetallic rare-earth metal complexes showed a higher polymerization activity than the corresponding monometallic species mostly resulting from the cooperative effect.

Maximization of furanic compounds formation by dehydration and hydrogenation of xylose in one step over SO3–H functionalized H-β catalyst in alcohol media

Abstract: Furanic compounds such as furfural (FUR); furfuryl alcohol (F Alc) are important renewable platform chemicals can be used as such or further convert for preparation of other value added products such as Levulinic acid (LA), Alkyl Levulinates, 2-Methyltetrahydrofuran (MTHF), and Tetrahydrofuran (THF) etc Sulfonated H-β zeolite was successfully prepared and used for the synthesis of furanic compounds especially FUR and F Alc from d -xylose in one step using isopropanol as alcohol media Prepared catalyst was well characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), BET, NH3-Temperature programmed desorption (TPD) and carbon-hydrogen-nitrogen-sulfur analysis (CHNS) It was found the total acid amount was increased with increase in sulfur loading which confirmed the sulfonic acid group (SO3–H) was successfully grafted onto zeolite structure 3 wt% H-β–SO3–H catalyst with optimized reaction parameters of 150 °C, 7 h, 25 wt% catalyst loading was tuned to get the highest furanic compound yield of 885% (FUR 768% + FAlc 117%)The reusability study confirmed that there was a marginal drop of ~25% after 3 recycle runs

A Simultaneous Conversion and Extraction of Furfural from Pentose in Dilute Acid Hydrolysate of Quercus mongolica Using an Aqueous Biphasic System

Abstract: This study optimizes furfural production from pentose released in the liquid hydrolysate of hardwood using an aqueous biphasic system. Dilute acid pretreatment with 4% sulfuric acid was conducted to extract pentose from liquid Quercus mongolica hydrolysate. To produce furfural from xylose, a xylose standard solution with the same acid concentration of the liquid hydrolysate and extracting solvent (tetrahydrofuran) were applied to the aqueous biphasic system. A response surface methodology was adopted to optimize furfural production in the aqueous biphasic system. A maximum furfural yield of 72.39% was achieved at optimal conditions as per the RSM; a reaction temperature of 170 °C, reaction time of 120 min, and a xylose concentration of 10 g/L. Tetrahydrofuran, toluene, and dimethyl sulfoxide were evaluated to understand the effects of the solvent on furfural production. Tetrahydrofuran generated the highest furfural yield, while DMSO gave the lowest yield. A furfural yield of 68.20% from pentose was achieved in the liquid hydrolysate of Quercus mongolica under optimal conditions using tetrahydrofuran as the extracting solvent. The aqueous and tetrahydrofuran fractions were separated from the aqueous biphasic solvent by salting out using sodium chloride, and 94.63% of the furfural produced was drawn out through two extractions using tetrahydrofuran.

Molecular interaction studies in binary mixtures of tetrahydrofuran with arene-substituted alcohols: acoustic and volumetric study

Abstract: In the present investigation, density and speed of sound have been reported for binary liquid mixtures of tetrahydrofuran with benzyl alcohol and 4-methoxybenzyl alcohol over the entire com...

Synthesis and properties of degradable gels and porous polymers including acetal group in the network structure by addition reaction of multi-functional phenols and divinyl ether compounds

Abstract: Gels containing acetal group have been synthesized by addition reaction of multi-functional phenols, 1,1,1-tris(4-hydroxyphenyl)ethane (THPE) or tannic acid (TA) and divinylethers, diethylene glycol divinyl ether (DEGVE) or polyethylene glycol divinyl ether (PEGVE) in tetrahydrofuran (THF) or 1,4-dioxane (DO) using pyridinium p-toluenesulfonate as a catalyst under nitrogen atmosphere. The gels synthesized from DEGVE showed higher Young’s modulus, breaking stress, and lower breaking strain than the gels synthesized from PEGVE. The gels in DO showed higher mechanical properties than those in THF due to the high affinity between the network structure and the solvent used. The gels with TA showed lower Young’s modulus than those with THPE derived from flexible molecular structure of TA. The reaction of THPE and PEGVE in acetonitrile induced phase separation, and yielded porous polymer formed by connected globules about 10 μm diameter. The dried porous polymers showed remarkable increase in the Young’s modulus in comparison with the corresponding gels in THF or DO. The gels and porous polymers were degraded under atmospheric conditions caused by hydrolytic degradation of acetal groups in the network structure. The present hydrolytic degradable materials would be applicable for drug carriers or sensors for humidity or water.

Catalytic Adipic Acid Production on Zeolites from Biomass-Derived Tetrahydrofuran-2,5-dicarboxylic Acid

Abstract: Adipic acid (AA) is an important precursor for the production of Nylon-66, and renewable routes for AA are being explored. Previously we have shown the use of HI and molecular H2 to be an effective...

Regulation of the Metal Center and Coordinating Anion of Mononuclear Ln(III) Complexes to Promote an Efficient Luminescence Response to Various Organic Solvents.

Abstract: A series of mononuclear lanthanide complexes [Ln(L1)(NO3)3], (Ln = Dy(III), 1; Tb(III), 3; and Eu(III), 4; L1 = (N1E,N2E)-N1,N2-bis((1-methyl-1H-benzo[d]imidazol-2-yl)methylene)cyclohexane-1,2-diamine) is obtained by reacting N-methylbenzimidazole-2-carbaldehyde (L2) and 1,2-cyclohexanediamine (L3) with Ln(NO3)3·6H2O under solvothermal conditions. L1 ligand is produced via an in situ Schiff base reaction of two molecules of L2 and one molecule of L3. The metal center Ln(III) is in a N4O6 environment formed by L1 and NO3-. NaSCN is added on the basis of 1 synthesis. One SCN- replaces one of the three coordinated NO3- anions in the 1 structure, and the complex [Dy(L1)(NO3)2(SCN)]·CH3CN (2) is synthesized. The complex 1 shows excellent luminescence response to petroleum ether (PET), an organic solvent. To the best of our knowledge, this study is the first to use a complex for sensing responses to PET. When the metal center is changed, the obtained mononuclear complexes 3 and 4 show an excellent luminescence response to tetrahydrofuran (THF). Lastly, 2 obtained by changing the coordinating anion shows an excellent luminescence response to dichloromethane. Herein, for the first time, we regulate the metal center and coordinating anion of lanthanide complexes to adjust the recognition and response of these complexes to different organic solvents.

Chiral Vanadyl(V) Complexes Enable Efficient Asymmetric Reduction of β-Ketoamides: Application toward (S)-Duloxetine.

Abstract: High-valent chiral oxidovanadium(V) complexes derived from 3,5-substituted-N-salicylidene-l-tert-leucine were used as catalysts in asymmetric reduction of N-benzyl-β-ketoamides. Among six different solvents, three different alcohol additives, and two different boranes examined, the use of pinacolborane in tetrahydrofuran (THF) with a t-BuOH additive led to the best results at -20 °C. The corresponding β-hydroxyamides can be furnished with yields up to 92% and an enantiomeric excess (ee) up to 99%. We have successfully extended this catalytic protocol for the synthesis of an (S)-duloxetine precursor.