Showing papers on "Tetrahydrofuran published in 2013"

Catalytic Reduction of Biomass-Derived Furanic Compounds with Hydrogen

Abstract: Furfural and 5-hydroxymethylfurfural (HMF) are important platform chemicals in biorefinery. Reduction of furfural or HMF with H2 over heterogeneous catalysts is the simplest way to convert the oxygen-rich compounds. However, the process can involve many types of reactions such as hydrogenation of the C═O bond, hydrogenation of the furan ring, C–O hydrogenolysis, rearrangement, C–C dissociation, and polymerization. Hydrogenation reactions are most studied in line with hydrogenations of other α,β-unsaturated aldehydes, and it becomes possible to produce each product selectively: furfuryl alcohol, tetrahydrofurfuryl alcohol, 2,5-bis(hydroxymethyl)furan, or 2,5-bis(hydroxymethyl)tetrahydrofuran. Total reduction of side substituents to give 2-methylfuran or 2,5-dimethylfuran is another well-known reaction. Rearrangement and C–O hydrogenolysis reactions have been recently investigated, and they can give useful products such as cyclopentanone, 1,5-pentanediol, and 1,6-hexanediol. Ongoing studies of the reaction ...

How do liquid mixtures solubilize insoluble gelators? Self-assembly properties of pyrenyl-linker-glucono gelators in tetrahydrofuran-water mixtures

Abstract: The self-assembly behavior of a series of glucono-appended 1-pyrenesulfonyl derivatives containing α,ω-diaminoalkane spacers (Pn, where n, the number of methylene units separating the amino groups, is 2, 3, 4, 6, 7, and 8) in v:v tetrahydrofuran (THF):water mixtures is examined at room temperature. The Pn at 2 w/v % concentrations do not dissolve in either THF or water at room temperature. However, the Pn can be dissolved in some THF:water mixtures, and they form gels spontaneously in other compositions without dissolving completely. The self-assembly of the Pn in the liquid mixtures has been investigated using a variety of techniques. The particle sizes of the Pn in their solutions/sols, critical gelation concentrations, microstructures, thermal and mechanical stabilities of the gels, and molecular packing modes of Pn molecules in their gel networks are found to be very dependent on the composition of the liquid mixtures. Correlations between the self-assembly behavior of the Pn and the polarity of the liquid mixtures, as probed by E(T)(30) and Hansen solubility parameters, yield both qualitative and quantitative insights into why self-assembly of the Pn can or cannot be achieved in different liquid compositions. As revealed by UV-vis and fluorescence spectroscopy studies, π-π stacking of the pyrenyl groups occurs as part of the aggregation process. Correlations between the rheological properties of the gels and the Hansen solubility parameters of the Pn and the solvent mixtures indicate that hydrogen-bonding interactions are a major contributor to the mechanical stability. Overall, the results of this study offer a new strategy to investigate the balance between dissolution and aggregation of molecular gelators. To the best of our knowledge, this is the first example of the spontaneous formation of molecular gels without heating by placing gelators in mixtures of liquids in which they are insoluble in the neat components.

Methanol incorporation in clathrate hydrates and the implications for oil and gas pipeline flow assurance and icy planetary bodies

Abstract: One of the best-known uses of methanol is as antifreeze. Methanol is used in large quantities in industrial applications to prevent methane clathrate hydrate blockages from forming in oil and gas pipelines. Methanol is also assigned a major role as antifreeze in giving icy planetary bodies (e.g., Titan) a liquid subsurface ocean and/or an atmosphere containing significant quantities of methane. In this work, we reveal a previously unverified role for methanol as a guest in clathrate hydrate cages. X-ray diffraction (XRD) and NMR experiments showed that at temperatures near 273 K, methanol is incorporated in the hydrate lattice along with other guest molecules. The amount of included methanol depends on the preparative method used. For instance, single-crystal XRD shows that at low temperatures, the methanol molecules are hydrogen-bonded in 4.4% of the small cages of tetrahydrofuran cubic structure II hydrate. At higher temperatures, NMR spectroscopy reveals a number of methanol species incorporated in hydrocarbon hydrate lattices. At temperatures characteristic of icy planetary bodies, vapor deposits of methanol, water, and methane or xenon show that the presence of methanol accelerates hydrate formation on annealing and that there is unusually complex phase behavior as revealed by powder XRD and NMR spectroscopy. The presence of cubic structure I hydrate was confirmed and a unique hydrate phase was postulated to account for the data. Molecular dynamics calculations confirmed the possibility of methanol incorporation into the hydrate lattice and show that methanol can favorably replace a number of methane guests.

Isolation of the Large {Actinide}38 Poly-oxo Cluster with Uranium

Abstract: By controlling the water content, a new poly-oxo-metalate species containing 38 uranium centers has been solvothermally synthesized in the presence of benzoic acid in tetrahydrofuran (THF). The {U38} motif contains a distorted UO2 core of fluorite type, stabilized by benzoate and THF molecules. This compound is analogous to the {Pu38} motif and was characterized by X-ray photoelectron spectroscopy and magnetic analyses.

Sustainable Solvent Systems for Use in Tandem Carbohydrate Dehydration Hydrogenation

Abstract: Monophasic separation-friendly solvent systems were investigated for the sustainable acid-catalyzed dehydration of fructose to 5-hydroxymethylfurfural (HMF). The HMF selectivity depends on both fructose conversion, temperature, and the amount of cosolvent present in the aqueous solvent mixture. Use of HMF-derived 2,5-(dihydroxymethyl)tetrahydrofuran (DHMTHF) or low-boiling tetrahydrofuran (THF) as co-solvents results in increased selectivity (>70%) to HMF at fructose conversions of ca. 80%. Analysis of the fructose tautomer distribution in each solvent system by 13C NMR revealed higher furanose fractions in the presence of these and other protic (tetrahydrofurfuryl alcohol) and polar aprotic co-solvents (DMSO) relative to water alone. Formation of fructosides and/or difructose anhydrides in the presence of the co-solvents causes lower selectivity at early reaction times, but reversion to fructose and dehydration to HMF at longer reaction times results in increasing HMF selectivity with fructose conversion...

Neutral and Cationic N‐Heterocyclic Carbene Zinc Adducts and the BnOH/Zn(C6F5)2 Binary Mixture – Characterization and Use in the Ring‐Opening Polymerization of β‐Butyrolactone, Lactide, and Trimethylene Carbonate

Abstract: A variety of N-heterocyclic carbene (NHC) zinc adducts of the type NHC–ZnMe2 [2a, NHC = 1,3-dimesitylimidazol-2-ylidene; 2b, NHC = 1,3-(2,6-iPr2Ph)2-imidazol-2-ylidene; 2c, NHC = 1,3-di-tert-butylimidazol-2-ylidene] and NHC–Zn(C6F5)2 [4a, NHC = 1,3-dimesitylimidazol-2-ylidene; 4b, NHC = 1,3-(2,6-iPr2Ph)2-imidazol-2-ylidene; 4c, NHC = 1,3-di-tert-butylimidazol-2-ylidene] were synthesized by reaction of the appropriate NHC ligand with ZnMe2 or (toluene)Zn(C6F5)2. The X-ray molecular structures of derivatives 2b, 4b, and 4c confirmed their adduct nature, and their bonding and geometrical parameters are influenced by the nature of the Zn–X group. The ionization reaction of the dimethyl Zn species 2a and 2b with the methide abstracting reagent B(C6F5)3 in the presence of tetrahydrofuran (THF) afforded the NHC–Zn organocations (1,3-dimesitylimidazol-2-ylidene)Zn(Me)(THF)2+ (3a+) and [1,3-(2,6-iPr2Ph)2-imidazol-2-ylidene]Zn(Me)(THF)+ (3b+) as dissociated MeB(C6F5)3– salts, as deduced from NMR spectroscopic data. All of these NHC–Zn compounds and BnOH/Zn(C6F5)2 were tested as ring-opening polymerization (ROP) initiators of β-butyrolactone (β-BL), rac-lactide (rac-LA), and trimethylene carbonate (TMC). Although cations 3a+ and 3b+ were both inactive ROP initiators, as they appear to decompose prior to any ROP activity, the NHC–Zn(C6F5)2 compounds readily mediate the ROP of β-BL, rac-LA, and TMC to afford the corresponding polymeric materials with a moderate level of control, as deduced from NMR, size-exclusion chromatography (SEC), and mass spectrometric MALDI-TOF data. In contrast, the use of the alcohol BnOH (instead of a NHC moiety) as a nucleophile for association with (toluene)Zn(C6F5)2 led to efficient, highly controlled, and immortal ROP of TMC and rac-LA with the formation of controlled chain length and narrowly disperse materials.

Tetrahydrofuran in TiCl4/THF/MgCl2: a Non-Innocent Ligand for Supported Ziegler–Natta Polymerization Catalysts

Abstract: While Ziegler–Natta (ZN) polymerization is one of the most important catalytic industrial processes, the atomic-scale nature of the catalytically active surface species remains unknown. Coupling high-resolution solid-state NMR spectroscopy with periodic density functional theory (DFT) calculations, we demonstrate that the major surface species in the ZN precatalyst corresponds to an alkoxy Ti(IV) surface species, which probably results from the ring-opening of tetrahydrofuran (THF) on a cationic Ti(IV) species.

Evidence for Iron Nanoparticles Catalyzing the Rapid Dehydrogenation of Ammonia-Borane

Abstract: A series of precatalysts of the general formula [Fe(NCMe)(L)(PPh2C6H4CH═NCHR-)2][BF4]2 (where L = CO or NCMe, and R = Ph or H) were tested for the dehydrogenation of amine-boranes. They have already been used in our lab for the transfer hydrogenation or direct hydrogenation of ketones and the oxidative kinetic resolution of alcohols. We compared a series of sterically- (R = H or Ph) and electronically- (L = NCMe or CO) varied precatalysts in both protic and aprotic solvents for the release of hydrogen from ammonia-borane (AB) and studied the products by NMR. At room temperature in tetrahydrofuran (THF) we optimized our systems, and achieved maximum turnover frequencies (TOF) of up to 3.66 H2/sec and 1.8 total H2 equivalents, and in isopropanol we were able to release a maximum of 2.9 equiv of H2 and reuse some of our catalytic systems. In previous mechanistic studies we provided strong evidence that the active species during transfer hydrogenation (TH) and oxidation catalysis are zerovalent iron nanoparti...

Effects of Additive Mixture (THF/SDS) on the Thermodynamic and Kinetic Properties of CO2/H2 Hydrate in Porous Media

Abstract: The separation of CO2 from fuel gas (CO2/H2) as hydrates was studied. In this investigation, the effects and mechanism thereof of the additive mixture (1, 2, 3, and 4 mol % tetrahydrofuran (THF), with 1000 mg/L sodium dodecyl sulfate) on the thermodynamic and kinetic properties of the hydrate in porous media were measured using an isochoric method, keeping the volume constant. The experimental results show that an increasing THF concentration increases the driving force for hydrate formation and decreases the hydrate induction time. The Langmuir constants of H2 and CO2 showed that H2 may occupy the small cavities of s-II hydrate in the H2–CO2–THF–H2O system. The presence of THF results in a drastic decrease of the hydrate phase equilibrium pressure. Higher THF concentrations correspond to lower hydrate phase equilibrium pressures, but the decrease in pressure with concentration slows when the THF concentration exceeds 3 mol %. An improved thermodynamic model was used to predict the hydrate phase equilibri...

Breakthrough in Synergists for Kinetic Hydrate Inhibitor Polymers, Hexaalkylguanidinium Salts: Tetrahydrofuran Hydrate Crystal Growth Inhibition and Synergism with Polyvinylcaprolactam

Abstract: A series of hexaalkylguanidinium salts have been synthesized, either from urea using the well-known Vilsmeier route or in a one-pot alkylation reaction using guanidinium chloride. The hexaalkylguanidinium salts are water-soluble up to the hexa-n-butyl derivative but sparingly soluble for the hex-n-pentyl or hexa-isopentyl derivatives. The ability of hexaalkylguanidinium salts to inhibit the growth of a tetrahydrofuran (THF) hydrate crystal has been investigated. The hexabutylated derivative gave excellent crystal growth inhibition, superior to the performance of the quaternary ammonium salt tetra(n-butyl)ammonium bromide (TBAB) and close to that of tetra(n-pentyl)ammonium bromide (TPAB). As the alkyl group is reduced in length to propyl and ethyl, the inhibition performance drops off radically. The superior inhibition performance of hexabutylguanidinium bromide was illustrated by testing its ability as a synergist for the well-known kinetic hydrate inhibitor (KHI), poly(N-vinylcaprolactam) (PVCap). In hig...

O-H···S hydrogen bonds conform to the acid-base formalism.

Abstract: Hydrogen bonding interaction between the ROH hydrogen bond donor and sulfur atom as an acceptor has not been as well characterized as the O–H···O interaction. The strength of O–H···O interactions for a given donor has been well documented to scale linearly with the proton affinity (PA) of the H-bond acceptor. In this regard, O–H···O interactions conform to the acid–base formalism. The importance of such correlation is to be able to estimate molecular property of the complex from the known thermodynamic data of its constituents. In this work, we investigate the properties of O–H···S interaction in the complexes of the H-bond donor and sulfur containing acceptors of varying proton affinity. The hydrogen bonded complexes of p-Fluorophenol (FP) with four different sulfur containing acceptors and their oxygen analogues, namely H2O/H2S, MeOH/MeSH, Me2O/Me2S and tetrahydrofuran (THF)/tetrahydrothiophene (THT) were characterized in regard to its S1–S0 excitation spectra and the IR spectra. Two-color resonantly en...

Air‐Stable, Low‐Toxicity Precursors for CuIn(SeS)2 Solar Cells with 10.1 % Efficiency

Abstract: CuIn(SeS)2 (CISeS) has been regarded as one of the most promising absorber materials for high-efficiency Cu-based thin-film solar cells because of its tunable band gap in the range of 1.0–1.5 eV and high absorption coefficient on the order of 10 cm . However, the highest conversion efficiency to be realized has been only 15.0% for CISe cells as compared to that of 20.3% for Cu(InGa)(SeS)2 cells. [5] The current deposition methods for high-efficiency CISeS cells are mainly based on vacuum methods, that is, co-evaporation or sputtering followed by selenization, which dramatically increase the manufacturing costs owing to the expensive vacuum equipment. Therefore, solution-based nonvacuum deposition methods have been receiving great interest recently because of their low cost and high throughput. Nanoparticle-based ink and molecular precursor-based solutions are two popular routes that are employed to fabricate CISeS solar devices. By using nanoparticle-based methods, conversion efficiencies of 2–8% have been reported for CISeS solar cells. However, the nanoparticlebased method involves complicated synthesis procedures and tedious purification processes. Many issues, such as yield, solubility, long-term stability, and removal of organic ligands etc., still need to be solved. Molecular precursor methods present another promising route, but only a hydrazine-based method has achieved great success, yielding an efficiency beyond 10%. Recently, CISeS cells with an efficiency of 12% have been reported for a hydrazine-based solution method by Mitzi et al., for which this efficiency is comparable to that of cells fabricated by vacuum-based methods. However, hydrazine is a highly toxic and explosive solvent, so mass production is not easy. In this context, seeking a safe precursor-based method utilizing solutions of low toxicity is highly desirable. In this paper, we present a simple and green solution-based processing route for the fabrication of a high-quality CISeS absorber layer. Low-cost Cu2O and In(OH)3 are used as the starting materials and dissolved in butyldithiocarbamic acid that is generated from carbon disulfide and butylamine in situ. By using a spin-casting and annealing process in Se vapor, crack-free and pinhole-free CuIn(SeS)2 thin films were achieved. The most efficient solar cell exhibits a power conversion efficiency (PCE) of 10.1% without antireflection coating. The formation mechanism of the Cu and In precursors is shown schematically in Figure 1a. Butyldithiocarbamic acid was first formed in ethanol from the reaction of carbon disulfide with 1-butylamine at room temperature. As an organic acid, butyldithiocarbamic acid can react with metal oxides or metal hydroxides, such as Cu2O and In(OH)3. [20] The Cu and In precursors were confirmed by FTIR spectroscopy, as shown in Figure S2. It is noteworthy that these molecularbased precursor solutions for Cu and In are highly soluble in ethanol, and a viscous liquid is obtained if all the ethanol is removed under vacuum. More importantly, these sticky precursors can be dissolved in many common organic solvents, including methanol, isopropanol, diethyl ether, toluene, chloroform, chlorobenzene, dimethylformamide (DMF), tetrahydrofuran (THF), and dimethyl sulfoxide (DMSO). In this paper, ethanol was chosen as the solvent for its lack of toxicity. Other small primary and secondary amines, such as ethylamine, propylamine, hexylamine, N-methylhexylamine, diethylamine, dibutylamine, monoethanolamine, and pyrrolidine can also be used to dissolve metal oxides or metal hydroxides. Note that these molecular-precursor solutions for Cu and In remain stable for several months in air and can be directly used to deposit CISeS thin films without additional purification. Note that only volatile CS2, butylamine, and ethanol are used in our system, so that carbon can be completely removed by utilizing a sintering process. The thermogravimetric (TG) profile for the Cu and In precursors is shown in Figure 1b. These Cu and In precursors are thermally stable up to 120 8C, for which the decomposition starts from at approximately 150 8C and ceases at approximately 360 8C. The precursor film was prepared by spin Figure 1. (a) The formation mechanism of Cu and In precursors. (b) Thermogravimetric (TG) analysis of the Cu and In precursors measured under a N2 atmosphere. Inset: the digital photograph of the mixed Cu and In precursors dissolved in ethanol (~0.4m in total metal).

Enantiospecific Total Synthesis of N-Methylwelwitindolinone D Isonitrile

Abstract: The welwitindolinone family of natural products (e.g., 1–2, Scheme 1) has attracted tremendous attention from the synthetic community over the past two decades.[1,2,3,4,5] Interest in these compounds stems from their promising biological profiles, in addition to their compact, yet daunting structures. Synthetic efforts toward the welwitindolinones have led to at least ten methods for building the bicyclo[4.3.1] core that is common to most of these natural products.[1,4] However, the sheer difficulty associated with late-stage manipulations has plagued most synthetic routes and only a few completed syntheses have been reported in recent years.[5] Scheme 1 Welwitindolinones 1 and 2. One exceptionally challenging synthetic target is N-methylwelwitindolinone D isonitrile (2).[6, 7] The compound possesses five stereocenters, two quaternary carbons, and a heavily substituted cyclohexyl ring. Compared to other related family members, 2 also possesses an ether linkage between C3 and C14. Thus, a successful synthesis of 2 would not only have to assemble the congested oxindole-fused bicyclo[4.3.1] framework, but would also have to allow for introduction of the ethereal linkage on the sterically congested face of the bicycle. Highlights of synthetic efforts toward 2 include the Wood group’s assembly of the spirocyclic oxindole[8] and Rawal’s elegant total synthesis of (±)-2 in 2011.[5a] Herein, we report our synthetic forays toward 2, which culminate in an enantiospecific synthesis. Our retrosynthetic plan for the synthesis of 2 is presented in Scheme 2. The natural product would be accessed from 3 via late-stage manipulations. In a key disconnection, the tetrahydrofuran ring would be installed from keto-oxindole derivative 4. Of note, the ability to elaborate 4 to 3 would hinge on our ability to perform chemoselective and diastereoselective manipulations adjacent to the two carbonyls. The cyclic carbamate was thought to be accessible using an intramolecular nitrene insertion reaction[9] involving oxindole substrate 5. Substrate 5 would be derived from ketone 6, which in turn can be readily prepared from known carvone derivative 7[10] in just four steps using our previously established procedure involving an indolyne cyclization.[5b,11] Scheme 2 Retrosynthetic analysis of 2. Our approach toward implementing the retrosynthetic plan is highlighted in Scheme 3. Indole 6 was converted to oxindole 8 using a one-pot oxidation/hydrolysis sequence. As the acidic conditions led to desilylation, reprotection of the alcohol was necessary to provide 9. Deuteride reduction and carbamoylation proceeded without event to furnish 5 in quantitative yield. To our delight, exposure of 5 to Ag-promoted nitrene insertion conditions[12,5e] furnished 10 in 70% yield. It should be noted that attempts to use the proteo analog of 5 gave only 44% yield of the corresponding insertion product, along with 19% of recovered ketone 9. Thus, consistent with our previous findings on an alternate substrate,[5e] the strategic use of deuterium minimizes an undesirable competitive reaction, thus giving synthetically useful yields of the desired insertion product 10. From 10, a standard deprotection/oxidation sequence delivered key intermediate 4. Scheme 3 Elaboration of 6 to keto oxindole 4; TBS=tert-butyldimethylsilyl, NBS=N-bromosuccinimide, DMAP=4-dimethylaminopyridine, DMF=dimethylformamide, THF=tetrahydrofuran, Tf=trifluoromethanesulfonyl, OAc=acetate, bathophenanthroline=4,7-diphenyl-1,10-phenanthroline, ... Many attempts to introduce the tetrahydrofuran ring from 4 were put forth. Unfortunately, efforts toward site-selective functionalization of one carbonyl over the other via enol ethers were unsuccessful. After considerable experimentation, it was found that the keto carbonyl could be α-functionalized first upon treatment of 4 with CuBr2 in THF at ambient temperature to yield 11 as a single diastereomer (Scheme 4). It was hoped that C3-oxidation would provide an alcohol intermediate that would cyclize to give the necessary tetrahydrofuran ring. However, upon treatment of 11 with C3 oxidation conditions,[5b] the desired oxidation and cyclization did not occur. Instead, we unexpectedly obtained cyclobutane 13 in high yield, presumably via direct cyclization of the oxindole enolate (see transition structure 12).[13] X-ray analysis of a single crystal of 13 validated our structural assignment.[14,7] Scheme 4 Unexpected formation of cyclobutane 13; THF = tetrahydrofuran. As a workaround, we opted to introduce a protected hydroxyl group directly onto C3 of substrate 11. Mn(OAc)3 was deemed a potential reagent for selective C3-acetoxylation, based on its use in benzylic acetoxylation reactions.[15] As shown in Table 1, treatment of oxindole 11 with Mn(OAc)3 in AcOH at 80 °C provided acetoxylated product 14 (entry 1). Interestingly, when the corresponding reaction was conducted at 150 °C, we obtained a 53% yield of 3, which possesses the desired tetrahydrofuran ring. Alternatively, 3 could also be prepared in one-pot by performing the acetoxylation at 80 °C, removing the volatiles, and exposing the crude intermediate to K2CO3 in MeOH and H2O at 70 °C. Table 1 Conversion of 11 to acetate 14 and cyclized product 3. We also explored the feasibility of directly converting keto oxindole 4 to 3 (Scheme 5). Of note, the Wood group was able to elegantly install a tetrahydrofuran ring from a keto oxindole substrate using basic conditions and O2.[8] Despite the modest yield, this key precedent laid the groundwork for additional experimentation. To our delight, we found that simple exposure of 4 to tetrabutylammonium fluoride in acetonitrile in the presence of air efficiently delivered 3.[16] In previous studies, we[17] and others[18] have found that TBAF/air can facilitate C3 oxidation of oxindoles containing the welwitindolinone scaffold, but the use of TBAF/air to build an ethereal linkage via double C-H functionalization was unknown. It should be noted that the use of other bases in place of TBAF, such as K2CO3 and Cs2CO3, also promoted the formation of 3, albeit in lower yields. It is likely that this efficient method for introducing the tetrahydrofuran ring proceeds by initial diastereoselective C3 oxidation, followed by cyclization.[19] Related C3-peroxy compounds have been observed in our studies[20] and in Wood’s.[8] Scheme 5 Double C-H functionalization of substrate 4 to install the tetrahydrofuran ring. To complete the total synthesis, it remained to elaborate the cyclic carbamate to the ketone and isonitrile functional groups present in 2 (Scheme 6). Unexpectedly, attempted hydrolysis of 3 led to cyclohexyl ring fragmentation, a process that was attributed to the reactivity of the ketone. To circumvent this, ketone 3 was reduced to alcohol 15 with LiAlH4. Fortunately, upon exposure of 15 to hydrolysis conditions, cyclohexyl ring fragmentation was not observed. Hydrolysis gave the desired diol intermediate, which was oxidized with IBX to provide diketone 16. Finally, formylation provided 17, which was directly exposed to standard dehydration conditions to deliver (+)-2. Scheme 6 Completion of (+)-2; THF=tetrahydrofuran, dioxane=1,4-dioxane, IBX=2-iodoxybenzoic acid, TFA=trifluoroacetic acid, DMSO=dimethylsulfoxide, Burgess reagent=methyl N-(triethylammoniumsulfonyl)carbamate. In summary, we have completed the enantiospecific total synthesis of N-methylwelwitindolinone D isonitrile. Several unexpected hurdles, including the formation of the unusual cyclobutane-containing compound 13 were overcome en route to the natural product. Our total synthesis features a double C-H functionalization event of keto oxindole 4 to introduce the tetrahydrofuran ring of 2 and is achieved in 17 steps from readily available carvone derivative 7.

Interactions of 1-Ethyl-3-methylimidazolium Trifluoromethanesulfonate Ionic Liquid with Alumina Nanoparticles and Organic Solvents Studied by Infrared Spectroscopy

Abstract: The interface between 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([EmIm][OTf]) ionic liquid (IL) supported on alumina nanoparticles and organic solvents (ethanol, tetrahydrofuran and acetonitrile) has been investigated using infrared (IR) spectroscopy. The investigations of these liquid–solid interfaces were preceded by separate studies of the IL in the different solvents and the IL supported on the alumina nanoparticles. IR analyses of the solvent–[EmIm][OTf] mixtures indicated that the triflate anion interacts differently with the three solvents. Comparison of the spectra of the IL supported on alumina with those measured for the corresponding solvent–IL mixtures indicates an interaction between the SO3 group of the anion and the alumina surface. In the organic solvent–IL–alumina systems, similar interactions between the IL and the oxide surface occur. The behavior of the IL/alumina interfaces was found to be consistent with a model where the ionic liquid structure is perturbed due to charge ...

Cyclization of some terpenic alcohols by phenylselenoetherification reaction

Abstract: Highly substituted tetrahydrofuran (THF)- and tetrahydropyran (THP)-type rings are formed through an acid- or base-catalyzed 5-exo and/or 6-endo cyclization of some natural terpenic alcohols (e.g., linalool, nerolidol, and α-terpineol) by an electrophile-mediated cyclization with PhSeCl and PhSeBr. The side chains of these cyclic ether products can be further transformed easily into a wide range of substrates owing to the versatile functionality of the double bond. Certain regioselectivity was noticed in these reactions. Nerolidol behaves like linalool in the reaction with PhSeX and affords predominantly THF derivatives, whereas α-terpineol affords THPs. Some Lewis bases (triethylamine, pyridine, 2,2′-bipyridine, and quinoline) and Lewis acids (SnCl2 and CoCl2) were used as additives, the presence of which increases the yields from 5–40 % to almost quantitative.

Comparison of Catalytic Characteristics of Biomass Derivates with Different Structures Over ZSM-5

Abstract: The conversion of three major biomass derivates was conducted in a quartz tubular fixed bed reactor over a ZSM-5 catalyst. As the model compounds of polyols, saturated furans and unsaturated furans, ethylene glycol (EG), tetrahydrofuran (THF) and furan were pyrolyzed to find out the influence of chemical structure on the catalytic characteristics. The effect of pyrolysis temperature (400 ∼ 650 °C), weight hourly space velocity (2.9 ∼ 15.5 h−1) and partial pressure (2.12 ∼ 20.49 Torr) on the feed conversion, product yield and selectivity were investigated. The hydrogen to carbon effective ratio (H/Ceff) was referred to, to analyze the capacity of biomass derivates being converted to chemicals (olefins and aromatics). The results showed that the existence of rings and C=C had great effect on the catalytic characteristics. The conversion of furan was much lower (mainly less than 60 %) than that of EG and TH,F which were close to 100 %. It was also found that the chemical yield of THF was slightly more than that of EG, which can be attributed to its relative higher H/Ceff of 1.5. Furan produced the highest coke yield, which was more than 15 %, whereas that of EG and THF was only around 5 %. The serious coking of furan led to the lowest chemical yield, which was less than 35 %. This study paves a way for the mechanism study on catalytic characteristics of biomass-derived feedstocks over zeolite catalysts.

Synthesis and structures of calcium and strontium 2,4-di-tert-butylphenolates and their reactivity towards the amine co-initiated ring-opening polymerisation of rac-lactide

Abstract: Calcium and strontium metals react with Hg(C6F5)2 and 2,4-di-tert-butylphenol (H-DBP) in tetrahydrofuran (THF) and 1,2-dimethoxyethane (DME) to give [Ca(DBP)2(THF)4] (1), [Ca2(DBP)4(DME)4(μ-DME)] (2), [Sr3(μ-DBP)6(THF)6] (3), and [Sr2(DBP)(μ-DBP)3(DME)3] (4). Compound 1 is a six coordinate trans-octahedral monomer, whereas in binuclear 2 two seven-coordinate Ca centres are bridged by a DME ligand. In 3 a central Sr is connected by three bridging DBP groups to each of two terminal Sr(THF)3 moieties, all metal atoms being six coordinate. Compound 4 has one six- and one seven-coordinate Sr, bridged by three DBP ligands, the former Sr also having a terminal DBP and a bidentate DME ligand and the latter two DME ligands. Complexes 2 and 4 act as ring-opening polymerisation (ROP) catalysts for the benzyl alcohol or benzylamine co-initiated ROP rac-lactide forming atactic alcohol- or amine-terminated polylactide H-[PLA]-XBn (X = O or NH) with reasonable control of molecular weight via an activated monomer propagation mechanism. Kinetic studies for BnNH2 found the unusual rate expression −d[LA]/dt = kp(Ae)[2 or 4]0[rac-LA]2[BnNH2]02.5 (kp(Ca) ≈ 1.7 × kp(Sr)). Preliminary studies suggest that [Y(DBP)3(THF)2] also catalyses amine or alcohol co-initiated ROP by an activated monomer mechanism without loss of a phenoxide ligand.

Poly(vinylalkanamide)s as Kinetic Hydrate Inhibitors: Comparison of Poly(N-vinylisobutyramide) with Poly(N-isopropylacrylamide)

Abstract: Kinetic hydrate inhibitors (KHIs) are water-soluble polymers that have been used for almost 20 years as a method to prevent the formation of gas hydrate plugs. Most classes of KHI polymers contain amide groups. We have now found a simple route to synthesize poly(N-vinylalkanamide)s (PVamides) from polyvinylamine. In this paper, we present results on the KHI performance of PVamides with varying alkyl chain lengths in the side group. This has been performed in tests with a structure-II-forming synthetic natural gas in high-pressure rocker cells and on tetrahydrofuran (THF) structure II hydrate crystal growth. The KHI performance of poly(N-isopropylacrylamide)s (PNIPAMs) and poly(N-vinylisobutyramide)s (PNVIBAs) at varying molecular weights was also compared, because these two polymers differ only in the orientation of the amide group.

Solventless Supramolecular Chemistry via Vapor Diffusion of Volatile Small Molecules upon a New Trinuclear Silver(I)-Nitrated Pyrazolate Macrometallocyclic Solid: An Experimental/Theoretical Investigation of the Dipole/Quadrupole Chemisorption Phenomena

Abstract: A comparative study on the tendency of a new trinuclear silver(I) pyrazolate, namely, [N,N-(3,5-dinitropyrazolate)Ag]3 (1), and a similar compound known previously, [N,N-[3,5-bis(trifluoromethyl)pyrazolate]Ag]3 (2), to adsorb small volatile molecules was performed. It was found that 1 has a remarkable tendency to form adducts, at room temperature and atmospheric pressure, with acetone, acetylacetone, ammonia, pyridine, acetonitrile, triethylamine, dimethyl sulfide, and tetrahydrothiophene, while carbon monoxide, tetrahydrofuran, alcohols, and diethyl ether were not adsorbed. On the contrary, 2 did not undergo adsorption of any of the aforementioned volatile molecules. Adducts of 1 were characterized by elemental analysis, IR, thermogravimetric analysis (TGA), Brunauer–Emmett–Teller (BET) surface area, and diffusion NMR measurements. The crystal structures of 1·2CH3CN and compound 3, derived from an attempt to crystallize the adduct of 1 with ammonia, were determined by single-crystal X-ray diffractometric...