Reaction Of Tetrahydrofuran Research Articles

New Interventions by silicone grease in synthesis

AbstractIn redox‐transmetallation protolysis (RTP) reactions in tetrahydrofuran (thf) between excess scandium or cerium metal, Hg(C6F5)2 and 3,5‐dimethylpyrazole (Me2pzH) in silicone greased Schlenk flasks, formation of the 3,5‐dimethyl‐1‐pyrazolyl(dimethyl)siloxide (Me2pzSiMe2O) ligand was observed. Thus the former reaction gave [Sc2(Me2pz)4(Me2pzSiMe2O)2] 1 in good yield, whilst the latter gave a mixture of [Ce4O(Me2pz)9(Me2pzSiMe2O)2] 2 a, [Ce4O(Me2pz)11] 2 b, both mixed oxidation state species, and the CeIV complex [Ce(Me2pz)4(Me2pzH)] 2 c.

Synthesis of (E)-α-hydroxyethyl-α,β-unsaturated aldehydes by the reaction of tetrahydrofuran and aromatic aldehydes

Although α-functionalized α,β-unsaturated aldehydes have important applications in biomedicine, there are few reports on their synthesis. In this article, a new domino reaction for the synthesis of (E)-α-hydroxyethyl-α,β-unsaturated aldehydes was introduced, in which tetrahydrofuran (THF) used as carbonyl block. The first step is an oxidation of THF to 2-hydroxytetrahydrofuran (HTHF) and then it was condensed with ethanolamine under acid catalysis to obtain imine intermediate, which was further isomerized to enamines and used as nucleophiles to attack aldehydes. This is a simple and efficient way for the preparation of (E)-α-hydroxyethyl-α,β-unsaturated aldehydes with notable advantages of a simple procedure, widespread availability of the substrates.

Thermal behavior of aminotrimethoxysilanphosphonate functionalized onto styrene-divinylbenzene copolymer

The chlorometylated styrene–divinylbenzene copolymer with different percent of divinylbenzene (code: S-6.7 DVB, S-12DVB, and S-15DVB) was functionalized with 3-hydroxybenzaldehyde for obtaining intermediated polymers. The aminotrimethoxysilanphosphonate groups were grafted by one-pot reactions in tetrahydrofuran using three components: polymers grafted with aldehyde groups (code: CHO-6.7, CHO-12, and CHO-15), 3-aminopropyltrimethoxysilane, diethylphosphite. The aminotrimethoxysilanphosphonate groups functionalized onto styrene-(6.7, 12, and 15%) divinylbenzene copolymer (code: PAF-6.7, PAF-12, and PAF-15) and evolution of the reaction were evidenced by FT-IR spectroscopy and porous structure by N2 adsorption-desorption, SEM microscopy. The thermal behavior of aldehydes and materials: PAF-6.7, PAF-12, and PAF-15 are different than initial polymer supports.

Switching from a Chromium(IV) Peroxide to a Chromium(III) Superoxide upon Coordination of a Donor in the trans Position.

O2 activation at a chromium(II) siloxide complex in propionitrileleads to a chromium(III) complex with an end-on bound superoxide ligand, while the reaction in tetrahydrofuran leads to a side-on peroxo chromium(IV) compound. The superoxide reacts faster with (2,2,6,6-tetramethylpiperidin-1-yl)oxyl hydroxylamine while the peroxide, unlike the superoxide, proved capable of deformylating aldehydes. The system was found to represent a unique case, where even a switching between the two structures can be achieved via the solvent; its ability to coordinate at the positiontrans to the O2 ligand is decisive, as supported by density functional theory studies. Altogether, the results show that subtle changes can determine for an initially formed metal-dioxygen adduct, whether it exists as a superoxide or a peroxide, which thus merits consideration in discussions on mechanisms and possible reaction routes.

Preparation of arylmagnesium/lithium from aryl bromides and their coupling and substitution reactions in tetrahydrofuran

One‐pot synthesis of 2‐aryltetrahydrofurans was achieved by a coupling reaction between arylmagnesium bromides prepared in situ and tetrahydrofuran under mild conditions. The reaction between ArBr and n‐BuLi gave unexpected butylbenzene derivatives in moderate yields.

The Role of Ate Complexes in the Copper-Mediated Trifluoromethylation of Alkynes.

Trifluoromethylation reactions have recently received increased attention because of the beneficial effect of the trifluoromethyl group on the pharmacological properties of numerous substances. A common method to introduce the trifluoromethyl group employs the Ruppert-Prakash reagent, that is, Si(CH3 )3 CF3 , together with a copper(I) halide. We have applied this method to the trifluoromethylation of aromatic alkynes and used electrospray-ionization mass spectrometry to investigate the mechanism of these reactions in tetrahydrofuran, dichloromethane, and acetonitrile as well as with and without added 1,10-phenanthroline. In the absence of the alkyne component, the homoleptic ate complexes [Cu(CF3 )2 ](-) and [Cu(CF3 )4 ](-) were observed. In the presence of the alkynes RH, the heteroleptic complexes [Cu(CF3 )3 R](-) were detected as well. Upon gas-phase fragmentation, these key intermediates released the cross-coupling products R-CF3 with perfect selectivity. Apparently, the [Cu(CF3 )3 R](-) complexes did not originate from homoleptic cuprate anions, but from unobservable neutral precursors. The present results moreover point to the involvement of oxygen as the oxidizing agent.

Synthesis, kinetic study, and applications of polyethyleneimine supported nano zirconium chromate in oxidation of furfuryl alcohol to corresponding carbonyl compound

The efficiency of highly branched polyethyleneimine has been investigated as a support for nano zirconium chromate and subsequent use as a heterogeneous oxidant for selective oxidation of furfuryl alcohol to furfural. These were synthesized using polyethyleneimine to produce a polymer coordinated nano zirconium, a noble and straightforward method for screening high catalytically active polymer nano composites. The one-step systematic derivatization of the polyethyleneimine scaffold led structurally correlated to the stabilization of zirconium nanoparticles and catalysis. Analysis of this polymeric reagent identified the zirconium chromate nano composite that was able to be effective to oxidation reaction in tetrahydrofuran under mild conditions due to the surface area of the nano zirconium chromate per unit volume. Capacity of the reagent and fixation of nano zirconium chromate is confirmed by ICP and atomic absorption technique. Morphology of this nano composite is investigated by SEM and TEM. The kinetic of oxidation of furfuryl alcohol, over heterogeneous catalyst, nano zirconium chromate in THF, were investigated. Power-law rate model was applied to describe the experimental results and obtain the orders of the reaction with respect to furfuryl alcohol, catalyst, and furfural, which were found to be 0.989, 0.991, and −0.68, respectively, with the activation energy of 76.78 kJ/mol.

Dissociative Adsorption of Diethyl Ether on Si(001) Studied by Means of Scanning Tunneling Microscopy and Photoelectron Spectroscopy

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).

Complex surface chemistry of an otherwise inert solvent molecule: tetrahydrofuran on Si(001).

The reaction of tetrahydrofuran (THF), an otherwise inert solvent molecule, on Si(001) was experimentally studied in ultra-high vacuum. Using scanning tunneling microscopy (STM) and photoelectron spectroscopy at variable temperature, we could both isolate a datively bound intermediate state of THF on Si(001), as well as the final configuration that bridges two dimer rows of the Si(001) surface after ether cleavage. The latter configuration implies splitting of the OC bond, which is typically kinetically suppressed. THF thus exhibits a hitherto unknown reactivity on Si(001).

Fluorescence properties of nanoaggregates of pyrene ammonium derivative and its photoinduced dissolution and reaction in tetrahydrofuran/aqueous solutions

We studied the fluorescence properties of nanoaggregates of pyrene ammonium derivative (PyAm) and their photoinduced dissolution and reaction in tetrahydrofuran (THF)/aqueous solution. The final concentration (dye concentration after reprecipitation) dependence of the fluorescence peak was measured. The fluorescence peak of PyAm that originated from the excimer is shifted to the long wavelength side increasing with the final concentration, which is ascribable to the characteristic fluorescence spectral changes depending on their size. The size-dependent fluorescence change in the nanoaggregates is related to some molecular conformation, packing, and elastic properties of the nanoparticles at the surface. To understand the fluorescence properties of the intermediates from aggregates to crystals is important for the studies of organic nanocrystals/aggregates prepared by the reprecipitation methods. We also determined the fluorescence spectra of the PyAm nanoaggregates in a THF/aqueous solution by photoinduced dissolution and reaction. It originated from the photochemical reaction between PyAm and THF. Changes in the perpendicular light scattering intensity by photoirradiation supports the photoinduced dissolution of PyAm in the THF/aqueous solution. These findings are important in the research field of photochemical reactions in organic nanocrystals.

Chemoselective Reduction of Functionalized 5-Nitroisoxazoles: Synthesis of 5-Amino- and 5-[Hydroxy(tetrahydrofuran-2-yl)amino]isoxazoles

Reduction by using SnCl2 of easily accessible 5-nitroisoxazoles substituted with an electron-withdrawing group (EWG) has been studied. Whereas the reaction in ethanol yielded 5-aminoisoxazoles, performing the reaction in tetrahydrofuran gave previously unknown 5-[hydroxy(tetrahydrofuran-2-yl)amino]isoxazoles. Both reduction procedures were optimized to afford the corresponding products in good to excellent yields. Some mechanistic details concerning the inclusion of the tetrahydrofuranyl moiety into the reaction product are discussed

Photolytic degradation of decabromodiphenyl ethane (DBDPE)

The photolytic degradation of decabromodiphenyl ethane (DBDPE), an alternative flame retardant to decabromodiphenyl ether, was investigated in a variety of matrixes (n-hexane, tetrahydrofuran, methanol/water, humic acid/water, and silica gel) by irradiation under ultraviolet light and in n-hexane under natural light. Photolytic degradation of DBDPE occurs in all the matrixes investigated within the irradiation period (<320min). The degradation experiments showed varied reaction rates, dependent on the matrixes, with increasing half-lives (t1/2) in the order of tetrahydrofuran (t1/2=6.0min)>n-hexane (t1/2=16.6min)>humic acid/water (30<t1/2<60)>silica gel (t1/2=75.9min)>methanol/water (t1/2>240min). The reaction in tetrahydrofuran, n-hexane, and silica gel matrixes can be described by the pseudo first order kinetics. Nevertheless, the matrixes have little effect on the degradation product distributions of DBDPE. A numbers of debrominated intermediates were identified. The degradation involves the initial formation of nona-BDPEs and the subsequent decomposition of these congeners to lower brominated congeners (octa- and hepta-BDPEs) within the irradiation time. To our knowledge, the present work is the first attempt to investigate the photolytic degradation kinetics and the identification of intermediates, as well as the degradation mechanism, during the degradation of DBDPE. Further research is needed to understand the photolytic degradation pattern of DBDPE in the natural environment.

Calciate-mediated intermolecular hydroamination of diphenylbutadiyne with secondary anilines

Calciate-mediated intermolecular hydroamination of diphenylbutadiyne with N-phenyl and N-isopropyl-substituted anilines yields E- and Z-isomers of the corresponding 1-anilino-1,4-diphenylbut-1-ene-3-yne. In the case of HNPh(2) solely heterobimetallic K(2)Ca(NPh(2))(4) is able to effectively catalyze this hydroamination reaction in tetrahydrofuran at elevated temperatures.

Synthesis of amphiphilic ABC triblock copolymers by single electron transfer nitroxide radical coupling reaction in tetrahydrofuran

AbstractA series of ABC triblock copolymers, that is, polyisoprene‐block‐polystyrene‐block‐poly(ethylene oxide) (PI‐PS‐PEO), PI‐block‐poly(tert‐butyl acrylate)‐block‐PEO (PI‐PtBA‐PEO), and PI‐block‐poly(acrylic acide)‐block‐PEO (PI‐PAA‐PEO) were obtained by combination of anionic technique, atom transfer radical polymerization (ATRP), and single electron transfer nitroxide coupling (SETNRC) reaction. Anionic polymerization of isoprene followed by end capping with ethylene oxide yielded hydroxyl‐terminated PI. After esterification, PI with Br end group was used as a macroinitiator to initiate the polymerization of styrene and tBA by ATRP that was then trapped by 2,2,6,6‐tetramethylpiperidine‐1‐oxyl (TEMPO) group in PEO by SETNRC reaction rapidly with high efficiency in tetrahydrofuran at room temperature. The effect of reaction time and polymer chain length on SETNRC reaction was discussed in detail. In the presence of Cu0/tris[2‐(dimethylamino)ethyl]amine, SETNRC between PI‐PS‐Br and PEO‐TEMPO was carried out with the efficiency of up to 91.6% in 2 h. With the increase in polymer chain length, the efficiency decreased fleetly. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Ion speciation driving chirality transfer in imidazolium-based camphorsulfonate ionic liquid solutions

The underlying principle of the chirality transfer in imidazolium-based camphorsulfonate ionic liquids is rationalized by linking catalytic results from the hydrogenation of [N-(3'-oxobutyl)-N-methylimidazolium] [(+)-camphorsulfonate] to [N-(3'-hydroxybutyl)-N-methylimidazolium] [(+)-camphorsulfonate] in tetrahydrofuran with electrolyte theory by the help of dielectric relaxation spectroscopy. Using this approach we are able to explain why the maximum of the enantiomeric excess of the hydrogenation reaction in tetrahydrofuran is found at a medium concentration of 0.15 mol L(-1), whereas it declines at both, lower and higher concentrations. Dielectric spectra in the concentration range between 0.05 and 1.0 mol L(-1) reveal a solute mode due to dipolar ion pairs and larger dipolar ion clusters. They verify that at very low concentrations the ionic liquid ions are fully solvated with an increasing tendency to form neutral ion pairs with increasing concentration. Already at 0.025 mol L(-1) the degree of dissociation reaches a minimum reflecting a maximum of neutral ion pair formation. With increasing ionic liquid concentration ordered ion clusters are formed by two and more ion pairs. At high concentrations these clusters collapse by dilution in the excess ionic liquid and the defined ion contact necessary for the chirality transfer is lost to a great extent.

Preparation of Organosoluble Silica−Polypeptide Particles by “Click” Chemistry

The synthesis of organo-soluble hybrid particles with a hydrophobic, α-helical polypeptide shell and silica core has been achieved by combining ring-opening polymerization and click chemistry. Alkyne end-terminated poly(γ-stearyl-α-l-glutamate) (alkyne-PSLG) was prepared by the ring-opening polymerization of the N-carboxyanhydride of γ-stearyl-α-l-glutamate using propargylamine as initiator. The molecular weight and structure of this polypeptide were characterized by GPC and MALDI, and the α-helical nature was established by 1H NMR and FTIR. Azide-functionalized silica particles (azido-silica) were prepared by the functionalization of silica particles with 3-bromopropyltrichlorosilane followed by nucleophilic substitution with sodium azide. The azide functionalization was confirmed by FTIR and XPS. Alkyne-PSLG was coupled to azido-silica by click reaction in tetrahydrofuran or toluene in the presence of pentamethyldiethylenetriamine and copper(I) bromide. Further characterization of the product using XPS, FTIR, and 1H NMR revealed that the grafted polypeptide retained its α-helical nature and formed colloidal particles that readily dispersed in organic solvents. These hydrophobic, polypeptide-functionalized particles can serve as model systems in studies of colloid dynamics and/or crystallization. They may also find use in investigations designed to model enzyme activation or the properties of hydrophobic proteins in cell membranes.

Influence of the Solvent on the Formation of New Tin(II) Methoxides Containing Thienyl Substituents: Crystal Structure and NMR Investigations

AbstractThe synthesis, structural characterization, and NMR studies of new tin(II) alkoxides with thiophene‐based substituents are presented. The reaction of ligand HO–C(C4H3S)3 (1) with bis(hexamethyldisilazyl)tin {Sn[N(SiMe3)2]2} in the ratio 2:1 in toluene yields the dinuclear compound {Sn[OC(C4H3S)3]2}2·2 toluene (2). The same reaction in tetrahydrofuran allows the isolation of two compounds: a dinuclear {Sn[OC(C4H3S)3]2}2·2 thf (3) and a mononuclear Sn[OC(C4H3S)3]2(thf) (4) molecule. The molecular structures of these tin(II) methoxides containing thienyl substituents 2–4 were investigated by single‐crystal X‐ray crystallography. The NMR spectra of solutions of {Sn[OC(C4H3S)3]2}2·2 toluene (2) or {Sn[OC(C4H3S)3]2}2·2 thf (3) and Sn[OC(C4H3S)3]2(thf) (4) are almost identical, showing only variations of the molar ratio of the dimeric and monomeric compounds.

Catalytic alkynone generation by Sonogashira reaction and its application in three-component pyrimidine synthesis

The Sonogashira alkynylation of acid chlorides can be efficiently conducted in less than an hour by performing the reaction in tetrahydrofuran as a solvent and in the presence of one stoichiometrically necessary equivalent of triethylamine as a base. This approach also opens new avenues for consecutive one-pot multicomponent reactions. As an example, the one-pot three-component pyrimidine synthesis illustrates the versatility of this modified Sonogashira protocol as an entry to diversity-oriented heterocycle synthesis in a one-pot fashion. The protocol can be completed within a few hours.

Low-temperature chemical solution route for ZnO based sulfide coaxial nanocables: generalsynthesis and gas sensor application

A novel chemical solution approach has been developed to synthesize ZnO based sulfide coaxialnanocables such as ZnO/ZnS and ZnO/CdS by chemical reaction in tetrahydrofuran (THF;C4H8O), in whichsulfur, NaBH4 and ZnCl2 or CdCl2 were used as reactants and ZnO nanorods were used as the template at room temperature.The morphology and structure of ZnO/ZnS and ZnO/CdS coaxial nanocables havebeen characterized by transmission electron microscopy (TEM), field emissionscanning electron microscopy (FESEM), x-ray powder diffraction (XRD), x-rayphotoelectron spectroscopy (XPS) and Brunauer–Emmett–Teller (BET) analysis.Furthermore, the as-prepared ZnO/CdS coaxial nanocables have been applied asNH3 gas sensors at room temperature with superior sensitivity, good reproducibility and a shortresponse/recovery time. Finally, a first explanation for the improved performance of theZnO/CdS coaxial nanocable based gas sensors has been presented.

2‘-Deoxyguanosine, 2‘-Deoxycytidine, and 2‘-Deoxyadenosine Adducts Resulting from the Reaction of Tetrahydrofuran with DNA Bases

A recent study showed that tetrahydrofuran (THF), a widely used solvent, is carcinogenic in experimental animals. Despite its carcinogenic activity, there is a paucity of information regarding cellular toxicity, biomolecular damage, and genotoxicity induced by THF. We describe here the structural characterization of adducts produced by the reaction of oxidized THF with 2'-deoxyguanosine (dGuo-THF 1 and dGuo-THF 2), 2'-deoxyadenosine (dAdo-THF), and 2'-deoxycytidine (dCyd-THF). Adducts were isolated from in vitro reactions by reverse-phase HPLC and fully characterized on the basis of spectroscopic measurements. The stable derivatives obtained by the reduction of adducts with NaBH(4) (the case of dGuo-THF 1, dCyd-THF, and dAdo-THF) and the stable adduct dGuo-THF 2 were used as standards for optimization of chromatographic separations for adduct detection in DNA through HPLC/ESI/MS-MS. Using this methodology, we successfully detected the four adducts in calf thymus DNA reacted with oxidized THF. The present study also provides evidence that rat liver microsomal monooxigenases oxidize THF to the reactive electrophilic compounds that are able to damage the DNA molecule, as indicated by a significant increase in adduct dGuo-THF 1 level when NADPH was added to the THF/microsomes/dGuo incubation mixtures. Our data point to DNA-THF adducts as possible contributing factors to the toxicological effects of THF exposure.