Showing papers on "Tetrahydrofuran published in 1990"
TL;DR: In this paper, the X-ray crystal structures of 1 and the related manganese compound Mn[N(SiMe3)2]2·2THF (5) are reported.
142 citations
TL;DR: In this paper, a simple OPLS model was adopted and parameterized to yield good descriptions of bimolecular and ion-molecule complexes as well as to reproduce experimental thermodynamic properties of liquid ethers.
Abstract: Intermolecular potential functions have been developed for use in computer simulations of alkyl ethers. The simple OPLS model was adopted and parameterized to yield good descriptions of bimolecular and ion-molecule complexes as well as to reproduce experimental thermodynamic properties of liquid ethers. The principal testing featured Monte Carlo statistical mechanics simulations for liquid dimethyl ether (DME), ethyl methyl ether (EME), diethyl ether (DEE), and tetrahydrofuran (THF). Average errors of 1–3% are obtained for the computed densities and heats of vaporization including results for THF at pressures up to 5000 atm. The torsional motion about the central CO bonds in EME and DEE was included in the simulations using rotational potential functions fit to results of molecular mechanics (MM2) calculations. The liquid-state environment is found to have negligible effect on the conformational equilibria.
138 citations
TL;DR: The coordinated tetrahydrofuran in (MeC 5 H 4 ) 3 Ce(THF) can be removed by Me 3 Al in a Lewis acid-base reaction or by the "toluene-reflux method" to give base-free (meC 5H 4 )3 Ce which is a monomer in the gas phase though a tetramer in the solid state: monoclinic, P2 1 /a, with a=12497 (5) A, b=26002 (8), A, c=9664 (3
99 citations
TL;DR: In this article, the authors characterized poly(TiCl 4 (APPY-O)(THF)•THF (4) compounds by proton, carbon-13, and phosphorus-31 NMR spectroscopy.
Abstract: The compounds were characterized by proton, carbon-13, and phosphorus-31 NMR spectroscopy and by infrared spectroscopy. Crystallographic characterization of trans-[TiCl 4 (APPY-O)(THF)]•THF (4) revealed that the ylide adopts the cisoid conformation in the solid state. 4 crystallizes in the monoclinic space group P2 1 /n in a unit cell of dimensions a=15.735 (5) A, b=9.818 (3) A, c=19.992 (5) A, β=105.17 (2)°, and V=2981 (1) A 3 , with R F =0.0554 (RWF=0,0554) for 286 parameters and 2251 observed reflections having F 0 >5σ(F 0 ). The potential of these complexes for forming O-bound, orthometalated species is discussed
80 citations
TL;DR: In this paper, the electrochemical behavior of tetrahydrofuran (THF) and propylene carbonate (PC) was investigated in the absence of deliberately added electrolyte using ultramicroelectrodes to minimize the effects of solution resistance.
80 citations
TL;DR: In this article, β-Unsaturated nitroalkenes are readily reduced to the corresponding oximes in good yields using ammonium formate in the presence of palladium.
80 citations
TL;DR: In this article, a series of poly(ether/ester)s 1 based on poly(butylene terephthalate)1 and poly(ethylene glycol) is synthesized.
Abstract: A series of poly(ether/ester)s 1 based on poly(butylene terephthalate)1 and poly(ethylene glycol) is synthesized. 1H and 13C nuclear magnetic resonance, infrared and differential scanning calorimetry (DSC) measurements prove a block structure of the prepared copolymers. The DSC curves suggest the existence of a three-phase morphology — two amorphous phases for both polyether and polyester segments, and a crystalline phase for the polyester segments. Small angle X-ray scattering (SAXS) measurements lead to the same conclusion. The degree of crystallinity assigned to the polyester fraction differs insignificantly and is similar to that of the homopolymer. SAXS data show approximately the same long spacing for all crystallizable copolymers. The tensile parameters of the studied polymers are similar to those of available commercial products based on poly(butylene terephthalate) and poly(tetrahydrofuran).
78 citations
TL;DR: In this article, the authors measured the solvatochromic hydrogen bond (HB) donor acidity (αm) values for aqueous mixtures of methanol, ethanol, isopropanol, acetonitrile and tetrahydrofuran.
76 citations
TL;DR: In this paper, a study of several factors, i.e. ligand, solvent, counterions, order and rate of additions, temperature, and the nature of Grignard reagents, that influence the regio- and enantioselectivities is given.
Abstract: Various chiral zinc(II) complexes catalyze the asymmetric 1,4-addition of Grignard reagents to α,β-unsaturated ketones with high chemoselectivities (yields of 1,4-adducts, 83-99%), high regioselectivities (1,4/1,2 ratios up to 499) and modest enantioselectivities (ee up to 33%). A study of several factors, i.e. ligand, solvent, counterions, order and rate of additions, temperature, and the nature of Grignard reagents, that influence the regio- and enantioselectivities is given. Based on the addition of isopropylmagnesium halides to 2-cyclohexenone as a model reaction, it was established that the highest enantioselectivities are reached with in situ prepared zinc complexes derived from optically active diamino alcohol ligands using lithium bases in tetrahydrofuran as the solvent. A mechanistic rationalization is given.
70 citations
TL;DR: In this article, an electrochemical analysis of a series of porphycenes and metalloporphyceners in tetrahydrofuran, N,N-dimethylformamide, and dichloromethane is reported.
Abstract: An electrochemical analysis of a series of porphycenes and metalloporphycenes in tetrahydrofuran, N,N-dimethylformamide, and dichloromethane is reported. This analysis combined the use of polarographic, steady-state voltammetric, cyclic voltammetric, and spectroelectrochemical methods. The free-base porphycenes studied were porphycene (H 2 Pc), 2,3,6,7,12,13,16,17-octaethylporphycene (H 2 OEPc), 2,7,12,17-tetra-n-propylporphycene (H 2 TPrPc), and its tetrabromo derivative, respectively
66 citations
TL;DR: In this paper, the X-ray structure of crystalline (1) shows a distorted trigonal bipyramidal Ca environment with the thf ligands in apical sites.
Abstract: Treatment of highly reactive, pyrophoric calcium or barium (obtained by co-condensation of the appropriate metal vapour and toluene) in tetrahydrofuran with (i) ArOH (Ca more reactive than Ba) affords the phenoxide [M(OAr)2(thf)n][M = Ca and n= 3 (1), or n= 0 after heating at 80°C and 10–2 Torr; M = Ba, n= 4], or (ii) R2NH (for M = Ca) yields [{Ca(NR2)(µ-NR2)(thf)}2][also obtained from (1)+ 2LiNR2 in n-C6H14; Ar = C6H2But2-2,6-Me-4; R = SiMe3)]; the X-ray structure of crystalline (1) shows a distorted trigonal bipyramidal Ca environment with the thf ligands in apical sites.
TL;DR: Stable, three-dimensional ordered complexes were formed from synthetically hydrated, highly ordered kaolinite (d(001) = 8.4 A) and several organic compounds as mentioned in this paper.
Abstract: Stable, three-dimensionally ordered complexes were formed from synthetically hydrated, highly ordered kaolinite (d(001) = 8.4 A) and several organic compounds. Removal of the intercalated organic compound by drying or by water washing recovered the 8.4-A hydrate with its ordered layer stacking essentially unchanged. Some of the complexes were stable for less than a day, whereas others appeared to be stable indefinitely. The compounds that formed ordered complexes were dimethylsulfoxide, form-amide, hydrazine-hydrate, 1,1-dimethylhydrazine, ethylene glycol, glycerol, and pyridine. Clay-organic complexes that were prepared from methanol, ethanol, 1- and 2-propanol, acetone, acetic acid, propionic acid, acetaldehyde, N-methylformamide, methylethyl ketone, tetrahydrofuran, and K-acetate were stable only if they were immersed in the intercalating medium and had little or no stacking order. Many of the organic compounds intercalated by the 8.4-A hydrate are not known to be intercalated by non-hydrated kaolinite either directly or indirectly. Isolated water molecules appear to be keyed into the ditrigonal holes formed by the basal oxygen of the silicate tetrahedra of the 8.4-A hydrate. These water molecules, referred to as “hole water,” and fluorine ions that had replaced ~20% of the inner-surface hydroxyls of the 8.4-A phase sufficiently altered the interlayer bonding to allow an expansion of the inner-layer spaces by a variety of guest molecules. The presence of these guest molecules between the clay layers not only changed the basal spacing and perturbed the infrared (IR) bands arising from the inner-surface hydroxyls, it also shifted the position of the IR band arising from the inner hydroxyl.
TL;DR: In this article, a phase transfer polymerization (PTMP) was proposed for elucidating a narrow molecular weight distribution of polyoxytetramethyleneglycol (PTMG).
Abstract: Polyoxytetramethyleneglycol (PTMG) can be directly prepared from tetrahydrofuran (THF) and water in the presence of heteropolyacids (HPA), without the hydrolysis step. The reaction is carried out by mixing two liquid phases: the THF phase and a heteropolyacid catalyst phase. In this reaction the molar ratio of water to a heteropolyacid (H2O/HPA) in the catalyst phase plays an important role in the THF polymerization activity and the molecular weight of PTMG. IR spectrometric studies revealed that THF is coordinated to a heteropolyanion through either a water molecule or a proton in the catalyst phase. The latter type of coordination bings about the activation of THF capable of initiating the ring-opening polymerization even in the presence of water at a lower acid strength. The PTMG prepared by this method has a narrow molecular weight distribution (Mw/Mn = 1.5 or less) and a number average molecular weight of 500–2000 which are requisite for the production of polyurethane elastomers. A new polymerization mechanism named “Phase Transfer Polymerization” is proposed for elucidating a narrow molecular weight distribution.
TL;DR: In this paper, the properties of poly(N-alkyl-3,6-carbazolediyl)s (PCZSs) were investigated in the presence of a catalytic Ni(0)-based system.
TL;DR: In this paper, a 2,3-bis(diphenylphosphinyl)-1, 3-butadiene (2,1′-bis)bicyclopropyl compound 4 has been prepared using double cyclopropanation using Me2S(CH2)O, followed by reduction using HSiCl3/NEt3.
Abstract: The title compound 4 has been prepared from readily available 2,3-bis(diphenylphosphinyl)-1,3-butadiene (1) through double cyclopropanation using Me2S(CH2)O to give 1,1′-bis(diphenylphosphinyl)bicyclopropyl (2), followed by reduction using HSiCl3/NEt3. Addition of sulfur to compound 4 yields the disulfide 5, and reaction with tetrahydrofuran – borane affords the 1:2 adduct with BH3 (6). Quaternization reactions with MeI or CH2I2 give the double quaternary salts 7 and 8, respectively. Single dehydrohalogenation employing nBuLi converts 8 into the cyclic semiylide salt 9. 4 is an excellent ligand for lowvalent late transition-metal cations. With PdI2 the 1:1 complex LPdI2 (10, with L = 4), and with [(CO)2RhCl]2 the ionic 2:1 complex L2Rh+Cl- (11) are obtained. Experiments with (CO)AuCl yield the 1:2 complex L(AuCl)2 (12), X-ray structure analyses were performed with single crystals of the disulfide 5, as well as the rhodium(I) and gold(I) complexes 11 and 12. 5 has a conformation between s-cis and s-trans with the PS functions pointing away from each other at opposite ends of the molecule. By contrast, in the gold(I) complex the ligand approaches an s-cis conformation, and through rotations about P–C and C–C bonds – as referred to the conformation of 5 – the metal atoms are brought into close contact: Au…Au = 3.085 A. Through temperature-dependent NMR investigations of compounds 5 and 12, and by comparison with values calculated or experimentally determined for related bicyclopropyl compounds (available in the literature), the energy of the Au…Au attraction has been estimated to be ca. 6 kcal/mol. Compound 11 features a square-planar, double-chelate cation.
Patent•
30 Mar 1990
TL;DR: The remover solution of as mentioned in this paper comprises from 35 to 80% by weight of an alcoholic solvent such as ethylene glycol monoethyl ether, from 10 to 40% of an organic solvent which is a halogenated hydrocarbon solvent, e.g., 1,2-dichlorobenzene and methylene chloride, and from 0.1 to 25% of a quaternay ammonium compound such as tetramethyl ammonium hydroxide.
Abstract: The remover solution of the invention comprises (A) from 35 to 80% by weight of an alcoholic solvent such as ethylene glycol monoethyl ether, (B) from 10 to 40% by weight of an organic solvent which is a halogenated hydrocarbon solvent, e.g., 1,2-dichlorobenzene and methylene chloride, an ether solvent, e.g., tetrahydrofuran, or an aromatic solvent, e.g., benzene and xylene, and (C) from 0.1 to 25% by weight of a quaternay ammonium compound such as tetramethyl ammonium hydroxide and trimethyl hydroxyethyl ammonium hydroxide. Different from conventional remover solutions which only can swell cured photoresist compositions, the inventive remover solution has a power to completely dissolve a cured photoresist layer to give a quite satisfactory result in the removing works of patterned photoresist layers in the manufacture of semiconductor devices.
TL;DR: In this article, the reaction of barium granules in tetrahydrofuran with either phenol or t-butyl alcohol yields phenoxide and tbutoxide aggregates that have been characterized in the crystalline state; they share a number of novel structural features, including the presence of a square-based pyramidal core supported by µ3 and µ2 phenoxide or butoxide ligands.
Abstract: The reaction of barium granules in tetrahydrofuran with either phenol or t-butyl alcohol yields phenoxide and t-butoxide aggregates that have been characterized in the crystalline state; they share a number of novel structural features, including the presence of a square-based pyramidal core Ba5(µ5-O) supported by µ3 and µ2 phenoxide or butoxide ligands.
TL;DR: The organometallic Lewis acid (η-cyclopentadienyl)bis(tetrahydrofuran)zirconium trichloride (2 ) was obtained from bis(cyclopentadiyl) zircarium dichloride and chlorine by means of a radical induced metal-Cp bond cleavage as mentioned in this paper.
TL;DR: In this paper, the tetrahydrofuran (THF) polymerization was initiated by difunctional peroxidic initiators, such as bis(4-bromomethyl benzoyl) peroxide and 2,5-dimethyl 2.5-di(4brommethyl benoyl peroxy)hexane.
TL;DR: In this article, the rates of dissociation of the N-B bonds in the title compounds were reexamined by the dynamic NMR technique to get further insight into the mechanism of the dissociation.
Abstract: The rates of dissociation of the N–B bonds in the title compounds were reexamined by the dynamic NMR technique to get further insight into the mechanism of dissociation. Entropies of activation were fairly large positive to suggest that the dissociation of a bond of ionic characters is the rate-limiting step. The rates of dissociation were generally larger in nonpolar solvents than in polar solvents, suggesting that the stabilization of the ground state by solvation was important in determining the activation energy for dissociation. Diethyl ether, tetrahydrofuran, and acetone gave larger rate constants of dissociation than those expected from their polarity. Participation of solvent molecules in the dissociation is discussed on the basis of these results. Introduction of various substituents indicated that steric effects as well as electronic effects affect the N–B bond energy.
TL;DR: Perfluoroalkyl iodides reacted with alkenes in acetonitrile solution containing catalytic amounts of an organophosphine under mild conditions to give the corresponding adducts in moderate to high yields as mentioned in this paper.
TL;DR: In this article, a reagent derived from lithium aluminum hydride and a metal salt or bromine in tetrahydrofuran below −30°C and successively treated with water or aldehydes to give rise to the corresponding 1H-perfluoroalkyl ketones (4) or α-fluoro-α perfluoro alkyl-β-hydroxy ketones(5), respectively, in moderate to good yields.
Abstract: Diethyl 1-substituted-1-perfluoroalkenyl phosphates (1), available from perfluoroalkyl ketones and sodium diethyl phosphite, were allowed to react with a reagent derived from lithium aluminum hydride and a metal salt or bromine in tetrahydrofuran below −30°C and successively treated with water or aldehydes to give rise to the corresponding 1H-perfluoroalkyl ketones (4) or α-fluoro-α-perfluoroalkyl-β-hydroxy ketones (5), respectively, in moderate to good yields. Copper(II) bromide, copper(I) bromide, and zinc chloride could be employed as the metal salt in the reaction. The phosphates also underwent reductive dephosphorylation with diisobutylaluminum hydride to generate the aluminum enolates of 1H-perfluoroalkyl ketones
TL;DR: In this paper, the authors used 1H NMR, IR spectroscopy, differential scanning calorimetry (DSC) and gel permeation chromatography (GPC) to characterize block copolymers.
Abstract: Poly(adipic anhydride) (PAA), poly(sebacic anhydride) (PSA) and poly(dodecanoic anhydride) (PDA) were prepared from the mixed anhydrides of diacids and ketene (in tetrahydrofuran (THF) solution), the mixed anhydrides being subjected to melt polycondensation. The polymerizations were carried out in the presence of diethyl zinc as a catalyst. The polymers were characterized by means of 1H NMR, IR spectroscopy, differential scanning calorimetry (DSC) and gel permeation chromatography (GPC). The polymer yields and the molecular weights of the polymers increased in the presence of catalyst. From these results a mechanism for the reaction is proposed. The highest melting temperature of the resultant polymers was obtained from PDA (Tpeak = 90°C). The heat of fusion was approximately 100 J/g (PDA). The number-average and weight-average molecular weights of the polyanhydrides were 18000 and 33000 respectively (PDA). Poly(anhydride)-b-poly(ethylene glycol) and poly(anhydride)-b-poly(tetramethylene glycol) copolymers were prepared from the mixed anhydrides of dodecanoic acid, poly(ethylene glycol)-succinic half-ester and poly(tetramethylene glycol)-succinic half-ester respectively. The block copolymers were characterized by means of 1H NMR, IR and GPC. The hydrolytic degradation of PDA has been studied in a buffered salt solution (pH 7·2) at 37°C by examining the changes in molecular weight, heat of fusion, mass loss and surface structure of melt-pressed PDA strips.
Patent•
16 Oct 1990
TL;DR: In a preferred embodiment, norhydrocodeinone is refluxed with sulfosalicyclic dimethylketal and delta-6-enol ether derivatives and is then converted entirely to the ether by the addition of dry tetrahydrofuran simultaneously with the removal of the thus produced ether as discussed by the authors.
Abstract: Families of antagonist-agonists and opiate narcotics are produced from norhydrocodeinone. In a preferred embodiment, norhydrocodeinone is refluxed with sulfosalicyclic dimethylketal and delta-6-enol ether derivatives and is then converted entirely to the ether by the addition of dry tetrahydrofuran simultaneously with the removal of the thus produced ether. The ether is then reacted with methanesulfonic acid and N-bromoacetamide to form the hydrobromide salt of the 7-bromodimethylketal derivative. From this derivative, a variety of products can be derived, including the novel further intermediate 14 hydroxynorcodeinone. The present invention enables derivation using a starting material which, unlike the starting materials of prior art processes, is available in the natural (-) or synthetic (+) form. Thus, the method of the present invention provides the only known route for the synthesis of (+) forms of various derivatives and intermediates, such as (+)-7-bromo-dimethylketal nordihydrocodeinone.
TL;DR: An efficient and convenient procedure for the hydrolysis of bile acid methyl esters is described by the addition of aqueous lithium hydroxide in methanol/dioxane (or tetrahydrofuran) at room temperature.
TL;DR: In this article disilylmethane is available in a four-step synthesis starting with phenylsilane, which is converted into chlorophenylmethylsilane by HCl/AlCl3 in a two-phase system using a phase transfer catalyst.
Abstract: Disilylmethane is available in a four-step synthesis starting with phenylsilane. This is converted into chlorophenylsilane by HCl/AlCl3. The reaction of PhSiH2Cl and dibromomethane with magnesium in tetrahydrofuran affords bis(phenylsilyl)-methane, which yields bis(bromosilyl)methane by treatment with anhydrous hydrogen bromide. (BrH2Si)2CH2 is converted into disilylmethane by reduction with LiAlH4 in a two-phase system using a phase-transfer catalyst. - Methyldisilane is available by alkylation of a monohalodisilane, XSi2H5 (X Cl, Br), with methyllithium in a high-boiling ether or by silylation of bromomethylsilane with silylpotassium. Due to secondary silylation reactions the overall yields of methyldisilane are low in all cases.
TL;DR: In this paper, Des copolymeres greffes methylphenyl silane-gr-THF sont prepares par greffage du THF sur le poly(methyl phenyl silANE) portant des groupes trifluoromethanesulfonate.
Abstract: Etude par RMN 1 H et 19 F du mecanisme d'amorcage. Des copolymeres greffes methylphenyl silane-gr-THF sont prepares par greffage du THF sur le poly(methyl phenyl silane) portant des groupes trifluoromethanesulfonate