Aqueous Tetrahydrofuran Research Articles

Transformations of 3-aryl-2-chloro-2-imidoylaziridines: novel entries to 4-chloro-2,5-diaryl-1 H-imidazoles and 2-chloro-2-acylaziridines

The reactivity of stereochemically defined 3-aryl-2-chloro-2-imidoylaziridines, an unexplored class of substituted aziridines, was investigated under various reaction conditions. 2-Chloro-2-imidoylaziridines underwent a novel thermal rearrangement by reflux in acetonitrile via C–C bond cleavage to 4-chloro-2,5-diarylimidazoles in high yield. Alternatively, a novel efficient entry toward 2-aroyl-2-chloroaziridines was based on the chemoselective hydrolysis of 2-chloro-2-imidoylaziridines with hydrochloric acid in aqueous tetrahydrofuran.

ChemInform Abstract: Convenient Synthesis of Pharmacologically Active ortho‐Substituted Biaryl Oxazolines via the Suzuki Reaction.

We describe an efficient protocol for the Suzuki–Miyaura synthesis of ortho-substituted biphenyl oxazolines from 2-(2-bromophenyl)-4,4-dimethyl-2-oxazoline and aryl boronic acids or aryl boronates. The Suzuki coupling is carried out in the presence of Pd(PPh3)4 and sodium carbonate in aqueous tetrahydrofuran. The scope and limitations of the reaction are discussed.

ChemInform Abstract: Diazo- and Azido-Functionalized Glutaraldehydes as Cross-Linking Reagents and Potential Fixatives for Electron Microscopy.

The synthesis of diazo and perfluorophenyl azide (PFPA) functionalized glutaraldehydes 7 and 13a-d as new cross-linking reagents for bioconjugation and potential fixatives for electron microscopy is reported. A key step is the generation of the 1,5-dialdehyde structures by oxidative cleavage of the corresponding cyclopentene epoxide using HIO4 in aqueous tetrahydrofuran. A model reaction between 3-substituted glutaraldehyde 14 and 6-aminohexanoic acid resulted in the formation of pyridinium ion containing products with UV spectra comparable to those observed with glutaraldehyde itself. Thus modification of glutaraldehyde in the 3-position most probably did not significantly change its reactivity with amines under chemical-fixation conditions. Fixation of red blood cells by 7 demonstrates that as a fixative, 7 is comparable to glutaraldehyde.

Convenient Synthesis of Pharmacologically Active Ortho-Substituted Biaryl Oxazolines via the Suzuki Reaction

We describe an efficient protocol for the Suzuki–Miyaura synthesis of ortho-substituted biphenyl oxazolines from 2-(2-bromophenyl)-4,4-dimethyl-2-oxazoline and aryl boronic acids or aryl boronates. The Suzuki coupling is carried out in the presence of Pd(PPh3)4 and sodium carbonate in aqueous tetrahydrofuran. The scope and limitations of the reaction are discussed.

SYNTHESIS OF SECONDARY ALCOHOL COMPOUNDS FROM SAFROLE AND METHYLEUGENOL

Synthesis of secondary alcohols compound from safrole and methyleugenol has been achieved through conversion of allyl group to alcohol.The reaction of safrole and methyleugenol with mercuric acetate in aqueous tetrahydrofuran, followed by in situ reduction of the mercurial intermediate by alkaline sodium borohydride produced secondary alcohol namely safryl alcohol (71.25%) and methyleugenil alcohol (65.56%). The structure elucidation of these products were analyzed by FTIR, 1H-NMR, 13C-NMR and MS. Keywords: Secondary alcohols; safrole; methyleugenol

Magnetic Alignment in Solid State and Temperature Hysteresis in Aqueous Tetrahydrofuran Solution for Tetrathiafulvaleno[18]annulenes

Tris(tetrathiafulvaleno)dodecadehydro[18]annulene-hexaesters have a multi-functionality that is very sensitive to small differences in the ester side-chain. Self-aggregation of the [18]annulenes in amphiphilic media such as THF-H(2)O (v/v, 1:1) either produce a fibrous structure or result in temperature hysteresis of the color and (1)H NMR signals. This temperature hysteresis in solution is due to both strong self-aggregation behavior and unique cluster formation in a binary solution of THF and water.

Anisotropy in Growth Kinetics of Tetrahydrofuran Clathrate Hydrate: A Molecular Dynamics Study

The growth kinetics of a tetrahydrofuran (THF) clathrate hydrate at the interface between the clathrate and an aqueous THF solution were investigated by means of a molecular dynamic simulation. The simulation was carried out for the interface of both the {100} and {111} planes of the THF clathrate. The simulation indicated the same anisotropic growth as that observed in real systems: the growth of the THF clathrate was much slower at the {111} interface than at the {100} interface. When the THF clathrate grew, THF molecules that were dissolved in the solution first were arranged at both large and small cage sites on the interface. Subsequently, the formation of cages by H(2)O molecules occurred in regions surrounded or sandwiched by those arranged THF molecules. As the formation of cages progressed, the THF molecules that had once been arranged at small cage sites gradually moved away from the sites, and finally the structure of the clathrate was completely formed. Simulation results strongly suggested that the rate-determining process for clathrate growth was the rearrangement of THF molecules at the interface from a disordered state to a state in which THF molecules were ideally arranged at large cage sites only. This rearrangement occurred much more slowly at the {111} interface than at the {100} interface, owing to the formation of a modified structure in which large and small cages were formed at opposite positions of the {111} interface. The anisotropic growth kinetics of the THF clathrate, which were obtained in this study, are consistent with the fact that growth shapes of THF clathrates in real systems are octahedral with flat {111} planes.

γ-Selective Cross-Coupling Reactions of Potassium Allyltrifluoroborates with Haloarenes Catalyzed by a Pd(0)/D-t-BPF or Pd(0)/Josiphos ((R,S)-CyPF-t-Bu) Complex: Mechanistic Studies on Transmetalation and Enantioselection

Cross-coupling between bromoarenes and [(E)-CH3CH=CHCH2BF3]K (2a) by a catalyst prepared from Pd(OAc)2 and D-t-BPF selectively provided γ-coupling products via SE2′ substitution. Mechanistic study of transmetalation revealed a heretofore unknown process, namely, formation of a highly electrophilic [Pd(Ar)(D-t-BPF)]+ before transmetalation with 2a. Thus, kinetic data in coupling of 4-substituted bromoarenes with 2a showed a linear positive correlation (ρ = −1.1) accelerated by donating substituents. This rate-determining role of transmetalation was further confirmed by kinetic data between oxidative adducts [Pd(Ar)(Br)(D-t-BPF)] and 2a that exhibited an analogous correlation with a negative ρ-value (−0.50). Theoretical study by density functional theory (DFT) calculation showed that transmetalation between [Ar−Pd]+ and 2a via an SE2′ (open) transition state is a slightly lower energy process than an SE2′ (closed) process. Allylic substitutions with chiral catalysts are the current topics for enantioselective C−C bond formation, but the catalysts that are effective for allylic nucleophiles have remained unexplored. Among the ligands screened, (R,S)-CyPF-t-Bu was found to achieve 77−90% ee for representative para- and meta-substituted bromoarenes and 2-bromo-1-alkenes in refluxing aqueous tetrahydrofuran (THF) or MeOH. To obtain mechanistic information on enantioselection, the mode of substrate coordination to a cationic phenylpalladium intermediate was calculated, that is, the reaction stage directly preceding the stereodetermining insertion step by DFT calculation. A stable adduct between [Pd(CyPF-t-Bu)(Ph)]+ and 2a located at the C−C double bond from its re-face yielding the experimentally observed R-product is preferred thermodynamically rather than the corresponding si-coordination.

Influence of carbohydrates on stability of papain in aqueous tetrahydrofuran mixture

AbstractBACKGROUND: The use of enzymes in organic solvents has extended the scale of their practical applications. Papain has been widely used in chemical syntheses because of its broad substrate specificity. The aim of the present study was to improve the stability of papain in aqueous tetrahydrofuran (THF) by using different saccharides. The effects of these carbohydrates on the structure of papain were followed by means of circular dichroism (CD) and fluorescence spectroscopic measurements.RESULTS: In contrast with most organic solvents, 60% (i.e. 600 mL L−1) THF practically inactivated the enzyme within 30 min. Sugars protected papain from THF‐induced inactivation in the sequence D‐ribose > D‐fructose > D‐glucose > D‐saccharose > D‐raffinose. Ribose at 1.6 mol L−1 proved the most effective stabiliser: in 60% THF in the presence of ribose, papain preserved about 55% of its initial activity after 2 h. Fluorescence and near‐UV CD spectroscopic measurements revealed local changes in the papain conformation. With decrease in the free amino group content of the enzyme, protein‐carbohydrate interactions (Schiff base formation) were detected.CONCLUSION: These results demonstrate that the catalytic activity and stability of papain may be increased in aqueous THF by using different carbohydrates, when a more compact structure of the enzyme is formed. Copyright © 2008 Society of Chemical Industry

Electrolytic debromination of PBDEs in DE-83 TM technical decabromodiphenyl ether

Electrochemical debromination of the commercial decabromodiphenyl ether flame retardant DE-83 TM in partly aqueous tetrahydrofuran (THF) solution gave lower brominated congeners by sequential loss of bromine atoms. Hydrodebromination was most facile for the most heavily brominated congeners. It involves initial electron transfer and proton transfer from water, rather than hydrogen atom abstraction from THF, as shown by experiments with deuterated water. The product distribution from electrolysis involves preferential loss of bromine meta- and para- to the ether linkage, comparable with the products of metabolism of BDE-209 in various organisms. Significantly, the environmentally relevant congeners BDE-47, BDE-99, and BDE-154 were not major products of debromination of BDE-209 by the electron transfer mechanism.

A Stereospecific Route to (Z)-Urocanic Acids

(Z)-Urocanic acid and its derivatives can be made stereo­specifically by ring-opening of pyrrolo[1,2-c]imidazol-5-ones in aqueous tetrahydrofuran.

Electrical and spectroscopic characterization of polyaniline–polyvinyl chloride (PANI–PVC) blends doped with sodium thiosulphate

Polyaniline is doped with sodium thiosulphate in aqueous tetrahydrofuran (THF) and the blended films have been prepared by changing the amount of doped polyaniline (PANI) in the fixed amount of polyvinyl chloride (PVC). The electrical conductivity of various samples of polyaniline–polyvinyl chloride (PANI–PVC) blends has been studied to see the effect of dopant in the temperature range 300–400 K. Mott's parameters are used to explain the conduction mechanism. Different parameters such as pre-exponential factor ( σ 0), activation energy (Δ E) and T 0 have also been calculated to see the effect of chemical doping. The crystallinity of the blends is explained on the basis of T 0. The calculated values of T 0 show that crystallinity increases with an increase of doped PANI in PANI–PVC blends. Fourier transform-infrared (FTIR) spectroscopy is done to explore the nature and interaction of dopant into the polymeric chain.

Reaction of Methyl‐4‐methylene‐2,3‐O‐isopropylidene‐β‐D‐ribofuranoside with N‐Bromosuccinimide in Aqueous Tetrahydrofuran.

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SURVISMETER, 2-IN-1 FOR VISCOSITY AND SURFACE TENSION MEASUREMENT, AN EXCELLENT INVENTION FOR INDUSTRIAL PROLIFERATION OF SURFACE FORCES IN LIQUIDS

Viscosities (η, N s m-2) and surface tensions (γ, N m-1) of methanol, ethanol, glycerol, ethyl acetate, n-hexane, diethyl ether, chloroform, benzene, carbon tetrachloride ( CCl 4), tetrahydrofuran (THF), dimethylformamide (DMF), dimethylsulfoxide (DMSO), acetonitrile, and formic acid have been measured with survismeter and compared with the data obtained by Ubbehold viscometer and stalagmometer, respectively. The ±1.1 × 10-5 N s m -2 and ±1.3 × 10-6 N m -1 deviations are noted in the data, in fact literature data of surface tension and viscosity are available to 2nd and 3rd place of decimals, respectively, while the survismeter measures them to 3rd and 4th place of decimals, respectively. The survismeter is 2-in-1 for viscosity and surface tension measurements together with high accuracies several times better than those of the separately measured data. Viscosities and surface tensions of aqueous DMSO, THF, DMF, and acetonitrile from 0.01 to 0.20 mol kg-1 and mannitol from 0.005 to 0.02 mol kg-1 have been measured with survismeter with ±1.2 × 10-5 N s m -2 and ±1.3 × 10-6 N m -1 deviations, respectively. The data are used for friccohesity and dipole moment determination, the lower viscosities, surface tension, and friccohesity values are noted for mannitol as compared to DMSO, THF, DMF, and acetonitrile solutions. The weaker molecular interactions are noted for mannitol. As compared to viscometer and stalagmometer individually, it is inexpensive and minimizes 2/3rd of consumables, human efforts, and infrastructure with 10 times better accuracies.

Apparent molar volumes and apparent molar heat capacities of aqueous tetrahydrofuran, dimethyl sulfoxide, 1,4-dioxane, and 1,2-dimethoxyethane at temperatures from 278.15 K to 393.15 K and at the pressure 0.35 MPa

We determined apparent molar volumes Vϕ at 278.15⩽(T/K)⩽368.15 and apparent molar heat capacities Cp,ϕ at 278.15⩽(T/K)⩽393.15 at p=0.35MPa for aqueous solutions of tetrahydrofuran at m from (0.016 to 2.5)mol·kg−1, dimethyl sulfoxide at m from (0.02 to 3.0)mol·kg−1, 1,4-dioxane at m from (0.015 to 2.0)mol·kg−1, and 1,2-dimethoxyethane at m from (0.01 to 2.0)mol·kg−1. Values of Vϕ were determined from densities measured with a vibrating-tube densimeter, and values of Cp,ϕ were determined with a twin fixed-cell, differential, temperature-scanning calorimeter. Empirical functions of m and T for each compound were fitted to our Vϕ and Cp,ϕ results.

Phase Relations and Binary Clathrate Hydrate Formation in the System H2−THF−H2O

Experimentally determined equilibrium phase relations are reported for the system H2-THF-H2O as a function of aqueous tetrahydrofuran (THF) concentration from 260 to 290 K at pressures up to 45 MPa. Data are consistent with the formation of cubic structure-II (CS-II) binary H2-THF clathrate hydrates with a stoichiometric THF-to-water ratio of 1:17, which can incorporate modest volumes of molecular hydrogen at elevated pressures. Direct compositional analyses of the clathrate phase, at both low (0.20 mol %) and stoichiometric (5.56 mol %) initial THF aqueous concentrations, are consistent with observed phase behavior, suggesting full occupancy of large hexakaidecahedral (51264) clathrate cavities by THF, coupled with largely complete (80-90%) filling of small dodecahedral (512) cages by single H2 molecules at pressures of >30 MPa, giving a clathrate formula of (H2) < or =2.THF.17H2O. Results should help to resolve the current controversy over binary H2-THF hydrate hydrogen contents; data confirm recent reports that suggest a maximum of approximately 1 mass % H2, this contradicting values of up to 4 mass % previously claimed for comparable conditions.

Air-water partitioning equilibrium of tetrahydrofuran in an activated sludge system

This study evaluate the effect of liquid tetrahydrofuran (THF) concentration and biomass content on the THF air-water partitioning equilibrium for a simulated activated sludge system. The equilibrium of the partition at the air-water interface is given by a partitioning coefficient (p c) = C g*/C L, where C g* denotes the gaseous concentration in equilibrium with the aqueous THF concentration (C L). Variations of p c with C L in static pure water are evaluated, and high solubility of THF in water caused p c values to drop as the C L increased from 29.81 ± 0.16 to 297.75 ± 2.28 mg/L at a constant temperature of 27°C. Meanwhile, the hydrophilicity of THF in water induced abiomass effect, causing p c to increase in the activated sludge liquor. Due to the co-effect of liquid THF concentration and biomass content, the p c values of THF for the liquor of mixed liquid suspended solid (MLSS) concentration = 1220 ± 86 mg/L and THF C L = 242.91 ± 69.09 mg/L increased 22.5% compared to those in the pure agitated water. The biomass effect on p c of hydrophilic VOC increases the gaseous VOC emission rate from the activated sludge facilities.

Role of the Nitro Group on Coal Solubilization in Aqueous Organic Solvents

Studies on the solubilization of two low-rank bituminous coals in aqueous organic solvents were conducted. The nitro group was introduced in the organic matrix of coal via oxidative nitration, using dilute nitric acid. The solubility of raw coals and the coals in which the nitro group was introduced were determined in aqueous acetone and aqueous tetrahydrofuran (THF). The experimental results reveal that introduction of the nitro group substantially enhanced the solubilization of coals in aqueous organic solvents. Heat treatment of the oxynitrated coal at 150 ± 10 °C in air caused the elimination of NO2 (as is experimentally evident) and a reduction of solubility in potent mixed solvents (from 49.5% to 25% in aqueous acetone, and from 56.2% to 29.3% in aqueous THF). The study reveals that the nitro groups present in oxynitrated coals had an important role in solubilizing it in aqueous organic solvents. The decrease in the nitro group was detected using the Fourier transform infrared (FTIR) difference spectra and was confirmed by the material balance data. A hypothetical route of the elimination of the nitro group and a possible mechanism for the reduction of solubility of oxynitrated coal, consequent upon its thermal treatment in the presence of air, have been presented for the first time, and these presentations are substantiated by FTIR spectra.

Synthesis and characterization of polyaniline-polyvinyl chloride blends doped with sulfamic acid in aqueous tetrahydrofuran

Abstract The temperature dependence of direct current (dc) conductivity was studied for various samples of polyaniline-polyvinylchloride (PANI-PVC) blended films. Polyaniline was doped with different concentrations of sulfamic acid in aqueous tetrahydrofuran (THF) and the blended films were prepared by varying the amount of doped PANI relative to a fixed amount of PVC. The dc conductivity of PANI-PVC blended films was measured to determine the effect of sulfamic acid (dopant) in the temperature range (300–400K). The mechanism of conduction is explained by a two-phase model. In order to evaluate the effect of the dopant, conductivity-derived parameters such as the pre-exponential factor (σ o) and the activation energy (ΔE) were calculated. The structural changes of polyaniline-PVC blended films were characterized by FTIR spectroscopy that explores information about the suitability of the dopant in the chemical doping process.

Caveolar Endocytosis and Microdomain Association of a Glycosphingolipid Analog Is Dependent on Its Sphingosine Stereochemistry

We have previously shown that glycosphingolipid analogs are internalized primarily via caveolae in various cell types. This selective internalization was not dependent on particular carbohydrate headgroups or sphingosine chain length. Here, we examine the role of sphingosine structure in the endocytosis of BODIPYtrade mark-tagged lactosylceramide (LacCer) analogs via caveolae. We found that whereas the LacCer analog with the natural (D-erythro) sphingosine stereochemistry is internalized mainly via caveolae, the non-natural (L-threo) LacCer analog is taken up via clathrin-, RhoA-, and Cdc42-dependent mechanisms and largely excluded from uptake via caveolae. Unlike the D-erythro-LacCer analog, the L-threo analog did not cluster in membrane microdomains when added at higher concentrations (5-20 microm). In vitro studies using small unilamellar vesicles and giant unilamellar vesicles demonstrated that L-threo-LacCer did not undergo a concentration-dependent excimer shift in fluorescence emission such as that seen with BODIPYtrade mark-sphingolipids with natural stereochemistry. Molecular modeling studies suggest that in d-erythro-LacCer, the disaccharide moiety extends above and in the same plane as the sphingosine hydrocarbon chain, while in L-threo-LacCer the carbohydrate group is nearly perpendicular to the hydrocarbon chain. Together, these results suggest that the altered stereochemistry of the sphingosine group in L-threo-LacCer results in a perturbed structure, which is unable to pack closely with natural membrane lipids, leading to a reduced inclusion in plasma membrane microdomains and decreased uptake by caveolar endocytosis. These findings demonstrate the importance of the sphingolipid stereochemistry in the formation of membrane microdomains.