Showing papers on "Tetrahydrofuran published in 1994"
TL;DR: An actinomycete capable of sustained aerobic growth on 1,4-dioxane was isolated from a dioxane-contaminated sludge samples and is capable of aerobic autotrophic growth on H2 and CO2.
Abstract: An actinomycete capable of sustained aerobic growth on 1,4-dioxane was isolated from a dioxane-contaminated sludge samples. The actinomycete, CB1190, grows on 1,4-dioxane as the sole carbon and energy source with a generation time of approximately 30 h. CB1190 degrades 1,4-dioxane at a rate of 0.33 mg of dioxane min-1 mg of protein-1 and mineralizes 59.5% of the dioxane to CO2. CB1190 also grows with other cyclic and linear ethers as the sole carbon and energy sources, including 1,3-dioxane, 2-methyl-1,3-dioxolane, tetrahydrofuran, tetrahydropyran, diethyl ether, and butyl methyl ether. CB1190 is capable of aerobic autotrophic growth on H2 and CO2.
184 citations
TL;DR: Sodium periodate oxidation of caffeic acid in aqueous solutions with pH ranging from 2 to 7 was investigated in this paper, and two products obtained at pH values lower than 4.6 approximately, were analyzed and isolated by reverse phase HPLC.
101 citations
TL;DR: Three different poly[(amino acid ester)phosphazenes] have been examined in order to investigate their possible use as drug delivery vehicles and comparisons of the hydrolytic decomposition and the small molecule release profiles of the polymers were made.
97 citations
TL;DR: In this article, a convenient procedure for the quantitative assay of alkyl, aryl, and vinyl Grignard reagent concentrations is described, through the combined use of menthol and 1,10-phenanthroline in dry tetrahydrofuran solution, vivid violet or burgundy end points materialize and are easily observed.
86 citations
TL;DR: The phase separation of 14 water-miscible polar solvents by salting-out using sodium chloride (4mol dm-3) was investigated in this article, where the phase separation properties of the separated organic solvent were determined by measuring ET(30)(=1.196×105/λ (kJmol 1)) and DII.
Abstract: Fourteen water-miscible polar solvents were investigated for the separation from their aqueous solutions by salting-out using sodium chloride (4mol dm-3). The following solvents showed the phase separation: acetone, acetonitrile, 1, 4- dioxane, tetrahydrofuran, 1-propanol, and 2-propanol. The chemical properties of the separated organic solvents were determined by measuring ET(30)(=1.196×105/λ (kJmol 1)) and DII.I(=1.196×105(λII-1-λI-1)(kJ mol-1))values from the spectral change of 2, 6-Biphenyl-4-(2, 4, 6-triphenylpyridinio)phenolate (DTP) and bis(1, 3-propanediolato)vanadium(IV) (VO(acac)2), where λ, λI, and λII denote the absorption maximum wavelengths (nm) of DTP and VO(acac)2. Solvent properties of acetone, acetonitrile, 1, 4-dioxane, and tetrahydrofuran were dramatically altered by the salting- out. Acceptability of the phase-separated solvents increased due to the dissolution of water molecules having large acceptor numbers. The ion-pair complex of tris(1, 10-phenanthroline)iron(II) chloride was easily extracted into the phase-separated acetonitrile by the salting-out. Some metal chelates of 1-(2-pyridylazo)-2-naphthol (Hpan) and 8- quinolinol (Hox), 5, 10, 15, 20-tetraphenylporphyrin (H2tpp), and ionic species (H2ox+, ox-, and H4tpp2+) were also extracted into 1, 4-dioxane. The raised donor and acceptor abilities of the phase-separated solvents allowed application to solvent extraction.
77 citations
TL;DR: In this article, the tetrahydrofuran with 2.2 equiv of a 1:1 sec-butyllithium/N,N, N,N',N'-tetramethyl-1,2-ethylenediamine complex at -90 o C gave o-LiC 6 H 4 CO 2 Li, which was treated with electrophiles to give o-RC 6 H4 CO 2 H (R=Me, SMe, Cl, Br) in good yields
Abstract: Treatment of PhCO 2 H in tetrahydrofuran with 2.2 equiv of a 1:1 sec-butyllithium/N,N,N',N'-tetramethyl-1,2-ethylenediamine complex at -90 o C gave o-LiC 6 H 4 CO 2 Li, which was treated with electrophiles to give o-RC 6 H 4 CO 2 H (R=Me, SMe, Cl, Br) in good yields
73 citations
TL;DR: In this article, the catalytic reactivity of maleic anhydride (MA), succinic anhydrides (SA), and their dimethyl esters (dimethyl maleate and dimethyl succinate) in the vapour phase hydrogenation to {gamma}-butyrolacetone (GBL) was investigated.
65 citations
TL;DR: No significant structural changes were observed by fluorescence studies even at the cosolvent concentrations where activity increases were significant and Stimulation of enzymatic activities was observed in all the cases at a specific concentration range ofcosolvent added which cannot be correlated either with log P or denaturation capacity.
Abstract: The activities of poyphenol oxidase, peroxidase, acid phosphatase and trypsin were measured in the presence of four different water miscible solvents, acetonitrile; N,N dimethylformamide; tetrahydrofuran and dioxane. Stimulation of enzymatic activities was observed in all the cases at a specific concentration range of cosolvent added which cannot be correlated either with log P or denaturation capacity. Also, no significant structural changes were observed by fluorescence studies even at the cosolvent concentrations where activity increases were significant.
63 citations
TL;DR: In this article, the relative stabilities of mixed aggregates of lithium diisopropylamide and lithium 2,2,6,6- tetramethylpiperidide with LiCl as well as theenolates derived from acetone, cyclohexanone, and 2,4-dimethylpentanone are described.
Abstract: Mixed aggregation of lithium dialkylamides with various LiX salts is studied by semiempirical (MNDO) computational methods. The relative stabilities of mixed aggregates of lithium diisopropylamide and lithium 2,2,6,6- tetramethylpiperidide with LiCl as well as theenolates derived from acetone, cyclohexanone, and 2,4-dimethylpentanone are described. The unsolvated forms are compared with the analogous structures solvated by tetrahydrofuran and hexamethylphosphoramide. The structural types studied include mixed cyclic dimers (R2NLi-LiX), trimers ((R2- NLi)z(LiX)2), and tetramers ((RzNLi)2(LiX)2); 3-rung ladders ((RzNLi)z(LiX)) and 4-rung ladders ((RzNLi)z- (Lix)~); two isomeric open dimer topologies corresponding to cyclic dimers fragmented at N-Li and X-Li bonds; triple ions (RzNLiX-//+Li). A complex interplay of steric effects appears to be the dominant influence on the mixed aggregate structures and relative stabilities.
58 citations
TL;DR: In this paper, the base-catalyzed condensation of benzyl isocyanoacetate with α-acetoxynitro compounds, or nitroalkenes, in refluxing tetrahydrofuran was described.
Abstract: Benzyl esters of 5-unsubstituted pyrrole-2-carboxylic acids were prepared in excellent yields by the base-catalyzed condensation of benzyl isocyanoacetate with α-acetoxynitro compounds, or nitroalkenes, in refluxing tetrahydrofuran. These pyrrolic products are important intermediates in the synthesis of porphyrins and related compounds
56 citations
TL;DR: The mono-and bis-(tetramethylphospholyl)uranium complexes [U(tmp)(Cl) 3 (L) 2 ] (tmp = C 4 Me 4 P, L = tetrahydrofuran or L 2 = dimethoxyet) as mentioned in this paper
TL;DR: In this article, the reaction of Na 2 [nido-7,8-Me 2 -7, 8-C 2 B 9 H 9 ] with [Ni 2 (μ-Br) 2 (η 3 -C 3 H 2 ) 2 ] or [Pt 2 (mbr) 2 η 3 c 3 H 5 ] + salts has been studied.
Abstract: Reaction of Na 2 [nido-7,8-Me 2 -7,8-C 2 B 9 H 9 ] with [Ni 2 (μ-Br) 2 (η 3 -C 3 H 2 ) 2 ] or [Pt 2 (μ-Br) 2 (η 3 -C 3 H 5 ) 2 ] - in thf (tetrahydrofuran) gives the anionic species [M(η 3 -C 3 H 5 )(η 5 -7,8-Me 2 -7,8-C 2 B 9 H 9 )] - (M=Ni or Pt) which have been isolated as their [NEt 4 ] 4 and [N(PPh 3 ) 2 ] + salts
TL;DR: The anions [X3U(µ-η7, η7-C7H7)UX3] and [X = NEt2 or BH4] have been obtained by treatment of UX4 with K[C 7H9] as discussed by the authors.
Abstract: The anions [X3U(µ-η7,η7-C7H7)UX3]–(X = NEt2 or BH4) have been obtained by treatment of UX4 with K[C7H9]; the cation [U(BH4)2(thf)5]+ was formed by protonation of [U(BH4)3(thf)3] with [NHEt3][BPh4] in tetrahydrofuran (thf).
TL;DR: In this paper, the reaction of bis(cyclopentadienyl)-2,3-dimethylzirconaindole, obtained by addition of 2-butyne to benzynesirconocene, with PCl 3, affords 1-chloro-2, 3-dimmethylphosphindole in a one-pot reaction and in moderate yield.
TL;DR: In this article, the transformation of alkynyl-, allyl-, and benzyltrimethylsilanes to the corresponding tributylstannanes is reported, initiated by the addition of tetrabutylammonium fluoride to a mixture of the silane and bis(tributyltin)oxide in tetrahydrofuran.
Abstract: : The transformation of alkynyl-, allyl-, and benzyltrimethylsilanes to the corresponding tributylstannanes is reported. The reaction is initiated by the addition of tetrabutylammonium fluoride to a mixture of the silane and bis(tributyltin)oxide in tetrahydrofuran. The stannanes are isolated in approx. quantitative yields after removal of the volatile bis(trimethylsilyl)oxide in vacuo. Silane, Stannane, Catalysis.
TL;DR: In this paper, a possible polar mechanism for 1:l RzZn(R’DAB) alkylation reactions is probed, for which organozinc radical anions [RZn[R]I*- and organozINC cations [R Zn[C]-+ have been suggested as the key intermediates.
TL;DR: In this paper, the authors investigated the mechanism of the reaction of transient silenes with alcohols in polar solvents, and concluded that the extracomplex proton transfer reaction most likely proceeds by a general base catalysis mechanism involving deprotonation of the complex by alcohol, followed by rapid protonation.
Abstract: Steady state and nanosecond laser flash photolysis techniques have been employed to investigate the mechanism af the reaction of transient silenes with alcohols in polar solvents. The photolysis of a homologous series of three aryldisilanes PhRR'SiSiMe3 (R, R' = methyl or phenyl) has been employed to generate transient 1,334 1-si1a)hexatriene derivatives which differ in the degree of aryYalky1-substitution at trivalent silicon. Rate constants for reaction of the silatrienes with methanol, methanol-0-d, trifluoroethanol, and acetic acid have been determined in acetonitrile, tetrahydrofuran, and isooctane solution. For the silatriene obtained from photolysis of pentamethylphenyldisilane, rate constants have also been measured for acetic acid-d, ethylene glycol, and 1,3-propanediol in acetonitrile solution. The results are consistent with a mechanism involving reversible formation of a silatriene-alcohol complex, followed by competing intracomplex and extracomplex proton transfer. The proton transfer steps are rate-determining when the alcohol is only weakly acidic, while complex formation is rate-determining for acidic alcohols or carboxylic acids. It is concluded that the extracomplex proton transfer reaction most likely proceeds by a general base catalysis mechanism involving deprotonation of the complex by alcohol, followed by rapid protonation. The products of (1,2)-, (1,4)-, and (1,6)-addition of methanol to the silatriene obtained from photolysis of pentamethylphenyldisilane in acetonitrile containing 0.15 M methanol have been isolated and identified, and the variation in product distribution with methanol concentration has been determined. The (1,2)-adduct predominates at very low methanol concentrations (50.01 M), where addition proceeds predominantly via the intracomplex proton transfer pathway. The ( 1,4)-adduct predominates at very high concentrations (2-5 M), which is proposed to be due to the involvement of methanol oligomers in the final, product-determining protonation step of the extracomplex proton transfer pathway.
01 Jan 1994
TL;DR: A commercial protease from Bacillus licheniformis efficiently catalyzed the transesterifica-tion of a diester of terephthalic acid and 1,4-butanediol in anhydrous tetrahydrofuran (THF).
Abstract: Lipases and proteases from various sources were tested in aromatic polyester synthesis in organic solvents. A commercial protease from Bacillus licheniformis efficiently catalyzed the transesterifica-tion of a diester of terephthalic acid and 1,4-butanediol in anhydrous tetrahydrofuran (THF). This protease was used as a catalyst in the synthesis of aromatic polyesters in THF. Oligomers with average molecular weights from 400 to 1000 daltons were obtained using various diols and aromatic diesters.
TL;DR: Imines 7, 11-13 were added to (1-alkynyl carbene)chromium complexes 6a-d to form {[2-(methyleneamino)ethenyl]-carbene}chromium complex 8a-D, 14aD, 15aD and 16aD in good to very good yields (63-98%) except for two cases (41-59%).
Abstract: Imines 7, 11-13 were added to (1-alkynylcarbene)chromium complexes 6a-d to form {[2-(methyleneamino)ethenyl]-carbene}chromium complexes 8a-d, 14a-d, 15a-d, 16a-d in good to very good yields (63-98%) except for two cases (41-59%). The carbene ligands of the latter compounds cyclize to 2H-pyrroles 9a-d, 17a-d, 18a-d, 19a-d upon heating in tetrahydrofuran solution to 50-55 o C
TL;DR: In this paper, the swelling volume of poly(N-isopropylacrylamide) (PIPAAm) gel in aprotic solvents (acetonitrile (AcN)-, tetrahydrofuran (THF)-, 1,4-dioxane (DO)- and dimethylsulfoxide (DMSO))-water mixtures was measured at 25°C.
Abstract: The swelling volume of poly(N-isopropylacrylamide) (PIPAAm) gel in aprotic solvents (acetonitrile (AcN)-, tetrahydrofuran (THF)-, 1,4-dioxane (DO)- and dimethylsulfoxide (DMSO))-water mixtures was measured at 25°C. The gel swollen in water shrank first and then reswelled with addition of the aprotic solvents. At an intermediate mole fraction (XDMSO) range of DMSO-water mixtures, the gel demonstrated a “reentrant” swelling phenomenon the hydrated gel shrank first on addition of a small amount of solvent, showed a typical wide reentrant transition, and gradually reswelled in the range near pure solvent. On the other hand, the gels in AcN-, THF-, and DO-water mixtures demonstrated a “reentrant-convex” swelling phenomenon: the gels reswelled after a reentrant phase transition in low Xorg (XAcN, XTHF and XDO), showed a maximum swelling in the intermediate Xorg region, and shrank again gradually in the high Xorg region. Such a swelling behavior of the gel was interpreted by correlating with solution properties of the aqueous aprotic solvent mixtures.
TL;DR: In this article, the reactions of dihalogenogermanes R 2 GeX 2 (X = halogen) with Mg and MgBr 2 in tetrahydrofuran produce the corresponding cyclotrigermanes (R 2 Ge) 3, and cyclotetragermanes 4, the preferred ring size of the products depends on the substituents at the germanium atom.
TL;DR: In this paper, the cyclic triamine 1,4,7-triisopropyl-1, 4, 7-triazacyclonononane (tiptacn) with formation of green triamines was obtained from a mixture of tetrahydrofuran, NaOCN, water, and methanol.
Abstract: Ti III (CH 3 CN) 3 Cl 3 in acetonitrile solution reacts with the cyclic triamine 1,4,7-triisopropyl-1,4,7-triazacyclononane (tiptacn) with formation of green [(tiptacn)Ti III Cl 3 ]. The chloro ligands in 1 are readily substituted by thiocyanate generating [(tiptacn)Ti(NCS) 3 ]. From a mixture of tetrahydrofuran, NaOCN, water, and methanol and 1 the complex [(tiptacn)Ti III (NCO) 2 (OCH 3 )] was obtained
01 Jan 1994
TL;DR: In this article, butyrates and acetates of heterocyclic alcohols like 3 - hydroxy tetrahydrofuran and - pyran, 3- and 4 - chromanol as well as the corresponding sulfur heterocycles were hydrolyzed using lipase from Candida rugosa (CRL) and from Pseudomonas cepacia, (PCL).
Abstract: The butyrates and acetates of heterocyclic alcohols like 3 - hydroxy tetrahydrofuran and - pyran, 3- and 4 - chromanol as well as the corresponding sulfur heterocycles were hydrolyzed using lipase from Candida rugosa (CRL) and from Pseudomonas cepacia, (PCL). Poor to excellent enantioselectivities were obtained depending on the structure of the substrates. An electrostatic amendment to the steric substrate model for PGL is proposed.
TL;DR: In this paper, a monomeric solvated ion pair with potassium unsymmetrically π-coordinated to an external ring of the polyaromatic system according to an X-ray structure determination was obtained.
Abstract: Crystallization of potassium(1+) and the radical ion coronene(1-) from a mixture of tetramethylethylenediamine (tmeda), tetrahydrofuran (THF), and diethyl ether yields a monomeric solvated ion pair 1 with potassium unsymmetrically π-coordinated to an external ring of the polyaromatic system according to an X-ray structure determination and in agreement with a MNDO theoretical investigation.
TL;DR: In this paper, a cycloaddition reaction of allyl-silane to α-keto esters afforded tri- and tetrasubstituted tetrahydrofurans with excellent stereoselectivity via 1,2-silyl migration in good yields.
Abstract: SnCl4 promoted [3+2] cycloaddition reactions of allylsilane to α-keto esters afforded tri- and tetrasubstituted tetrahydrofurans with excellent stereoselectivity via 1,2-silyl migration in good yields.
TL;DR: In this article, the solvatochromic hydrogen bond donor acidity parameter (αmix) of aqueous mixtures of methanol, acetonitrile, propan-2-ol and tetrahydrofuran were determined spectrophotometrically.
TL;DR: In this article, the synthesis of methyl 4-oxobutanoate with nitroethane in the presence of 4-dimethylaminopyridine, followed by treatment with acetic anhydride, afforded a nitroacetoxyester 10b.
TL;DR: In this paper, the miscibility of styrene copolymers of 4-vinylbenzenephosphonic acid diethyl ester (PSVBDEP) with poly(pvinylphenol) (PVPh) was studied by using DSC, FTIR, 31 P NMR, and 13 C NMR.
Abstract: The miscibility of styrene copolymers of 4-vinylbenzenephosphonic acid diethyl ester (PSVBDEP) with poly(p-vinylphenol) (PVPh) was studied by using DSC, FTIR, 31 P NMR, and 13 C NMR. Results indicated that the copolymer containing 4.3 mol % VBDEP units was immiscible with PVPh. For the PSVBDEP-7.5/PVPh blends, a single T g was observed when the content of PSVDEP-7.5 was at least 60wt %. Mixing of PSVDEP-13.3 with PVPh caused mutual precipitation in tetrahydrofuran. The complexes exhibited a single T g . Three hydrogen bond donors, hexafluoroisopropyl alcohol, phenol, and tert-butyl alcohol, were used to «calibrate» the strength of the -C 6 H 4 P(O)(OC 2 H 5 ) 3 group as an acceptor, and the characteristic parameter in the enthalpy-frequency shift relationship was determined