Showing papers on "Tetrahydrofuran published in 2002"
TL;DR: In this paper, a variety of Mg(AX 4n R n R n ) 2 complexes, where A = Al, B, Sb, P, As, Fe, and Ta; X = Cl, Br, and F; and R = butyl, ethyl, phenyl, and benzyl (Bu, Et, Ph, and Bz, respectively) in several solvents, including tetrahydrofuran (THF), 2Me-THF, 1-3 dioxolane, diethyl ether, and poly
Abstract: Magnesium can be reversibly deposited from ethereal solutions of Grignard salts of the RMgX type (R = alkyl, aryl groups, and X = halides: Cl, Br), and complexes of the Mg(AX 4-n R n' R' n ) 2 type (A = Al, B; X = Cl, Br; R, R' = alkyl or aryl groups, and n' + n = n). These complexes can he considered as interaction products between R 2 Mg bases and AX 3-n R n Lewis acids. The use of such complexes in ether solvents enables us to obtain solutions of reasonable ionic conductivity and high anodic stability, which can be suitable for rechargeable Mg battery systems. In this paper we report on the study of variety of Mg(AX 4-n R n ) 2 complexes, where A = Al, B, Sb, P, As, Fe, and Ta; X = Cl, Br, and F; and R = butyl, ethyl, phenyl, and benzyl (Bu, Et, Ph, and Bz, respectively) in several solvents, including tetrahydrofuran (THF), 2Me-THF, 1-3 dioxolane, diethyl ether, and polyethers from the glyme family, including dimethoxyethane (glyme), (CH 3 OCH 2 CH 2 ) 2 O(diglyme), and CH 3 (OCH 2 CH 2 ) 4 OCH 3 (tet-raglyme), as electrolyte solutions for rechargeable magnesium batteries. It was found that Mg(AlCl 4-n R n' R' n ) 2 complexes (R, R' = Et, Bu and n' + n = n) in THF or glymes constitute the best results in terms of the width of the electrochemical window (>2 V), from which magnesium can he deposited reversibly. These solutions were found to be suitable for use in rechargeable magnesium batteries. A variety of electrochemical and spectroscopic studies showed that these solutions have a complicated structure, which is discussed in this paper. It is also clear from this work that Mg deposition-dissolution processes in these solutions are far from being simple reactions of Mg/Mg +2 redox couple. The conditions for optimized Mg deposition-dissolution processes are discussed herein.
233 citations
TL;DR: In this article, the authors simplify extracts to facilitate the isolation of antibacterial compounds from the complex mixture of chemicals in the plant by using different extractants such as methylene dichloride, tetrahydrofuran, acetone, ethanol, ethyl acetate, methanol and water.
216 citations
TL;DR: In this article, the potential of solvent resistant nanofiltration to achieve non-destructive separation of homogeneous catalysts from organic solutions, allowing catalyst recycle, would be of considerable interest in commercial organic synthesis.
163 citations
TL;DR: In this paper, the Kirkwood-Buff integrals and the volume-corrected preferential solvation parameters for the first solvation shell of binary mixtures of tetrahydrofuran with many organic solvents, calculated from reported thermodynamic data at the temperatures for which these data were available, are reported.
Abstract: The Kirkwood–Buff integrals and the volume-corrected preferential solvation parameters for the first solvation shell of binary mixtures of tetrahydrofuran with many organic solvents, calculated from reported thermodynamic data at the temperatures for which these data were available, are reported. The co-solvents include c-hexane, methyl-c-hexane, n-heptane, i-octane, benzene, toluene, ethylbenzene, 1-chlorobutane, dichloromethane, 1,2-dichloroethane, chloroform, 1,1,1-trichloroethane, tetrachlorom-ethane, tetrachloroethene, hexafluoro benzene, ethanol, 1-propanol, 2-propanol, dibutyl ether, acetic acid, acetone, dimethyl sulfoxide, tetramethylene sulfone (sulfolane), acetonitrile, pyrrolidine, and triethylamine. The preferential solvation parameters of these mixtures are discussed in terms of the interactions that occur.
126 citations
TL;DR: In this article, the preparation and characterization of amphiphilic ABC miktoarm star copolymers based on polystyrene, and poly(ethylene oxide), poly(methyl acrylate) or poly(N-isopropylacrylamide) blocks are described.
Abstract: The preparation and characterization of amphiphilic ABC miktoarm star copolymers based on polystyrene, and poly(ethylene oxide), poly(methyl acrylate) or poly(N-isopropylacrylamide) blocks are described in this paper. First, macrotransfer agent polySt-MAh-S-C(S)Ph with maleic anhydride and a dithio group at one end of polymer chain was synthesized by the reaction of a dithio group at the end of the polystyrene with maleic anhydride (MAh) in tetrahydrofuran solution. The second, reversible addition−fragmentation chain transfer polymerization of methyl acrylate or N-isopropylacrylamide was carried out in the prescence of polySt-MAh-S-C(S)Ph and benzoyl peroxide. Finally, the anhydride group at the joint of two blocks was reacted with terminal hydroxyl group of poly(ethylene glycol methyl ether). The obtained ABC star copolymers were characterized by 1H NMR spectroscopy and gel permeation chromatography.
126 citations
TL;DR: In this article, a tetrabutylammonium-H2Ti4O9·xH2O intercalation compound was obtained by a guest exchange reaction between tetrabilized lammonium hydroxide and an intercalated H2Ti 4O 9·x H2O compound, and its dispersion state in aqueous and nonaqueous solutions were studied.
Abstract: A tetrabutylammonium–H2Ti4O9·xH2O intercalation compound was obtained by a guest exchange reaction between tetrabutylammonium hydroxide and an ethylammonium–H2Ti4O9·xH2O intercalation compound, and its dispersion state in aqueous and non-aqueous solutions were studied. Spontaneous exfoliation of H2Ti4O9·xH2O into colloidal nanosheets occurred when the tetrabutylammonium–H2Ti4O9·xH2O intercalation compound was dispersed in water, methyl alcohol, isopropyl alcohol, acetonitrile, N,N-dimethylformamide, dimethyl sulfoxide, and propylene carbonate, while exfoliation did not occur in tetrahydrofuran. A tetrabutylammonium–H2Ti4O9·xH2O film was obtained by a reassembly process by casting the colloidal suspension containing exfoliated nanosheets, while a H2Ti4O9·xH2O film was directly obtained by electrophoretic deposition. Thermal treatment of the electrophoretically deposited film led to an oriented TiO2(B) film with the (0k0) planes lying perpendicular to the substrate.
119 citations
TL;DR: The phase behavior of block copolymers of the ethers is influenced by both composition and topology (blocky versus random, block arrangement) as discussed by the authors, and it appears that the ether oxygens in polyethers enhance the solubility of such polymers, but only if the ether oxygen is in a readily accessible position.
Abstract: Polyethers of different composition and chain length were investigated with regard to their solubility in CO2. The nature of the monomeric unit, the degree of polymerization, the endgroup effect, the composition and the temperature significantly influence the solubility and thus the CO2 pressures required for miscibility. In general, it was found that polymers of propylene oxide are more ‘CO2-philic’ than analogs of either ethylene oxide or tetrahydrofuran. The phase behavior of block copolymers of the ethers is influenced by both composition and topology (blocky versus random, block arrangement). It appears that the ether oxygens in polyethers enhance the solubility of such polymers (relative to simple hydrocarbons) through specific interactions with CO2, but only if the ether oxygen is in a readily accessible position.
105 citations
TL;DR: In this article, an effective catalyst for the homo coupling of the Grignard reagent and alkyl halide when both alkyls groups are the same was proposed.
99 citations
TL;DR: A sterically hindered biphenol 2,2‘-(2-methoxybenzylidene)bis(4-methyl-6-tert-butylphenol) (MEBBP-H2) has been prepared by the reaction of o-anisaldehyde with 2-TERT-Butyl-4methylphenol in the presence of a catalytic amount of benzenesulfonic acid as mentioned in this paper.
Abstract: A sterically hindered biphenol 2,2‘-(2-methoxybenzylidene)bis(4-methyl-6-tert-butylphenol) (MEBBP-H2) (1) has been prepared by the reaction of o-anisaldehyde with 2-tert-butyl-4-methylphenol in the presence of a catalytic amount of benzenesulfonic acid. Further reaction of compound 1 with a stoichiometric amount of Me3Al in tetrahydrofuran produces a four-coordinated monomeric aluminum complex [(MEBBP)AlMe(THF)] (2). [(MEBBP)Al(μ-OBn)]2 (3) can then be synthesized by the reaction of 2 with 1 mol equiv of benzyl alcohol at ambient temperature. Compound 3 has demonstrated highly efficient activities toward ring-opening polymerization of e-caprolactone. The “living” and the “immortal” character of 3 has paved a way to synthesize as much as 256-fold polymer chains of poly(e-caprolactone) with a very narrow polydispersity index in the presence of a small amount of initiator. In addition, the polystyrene-b-poly(e-caprolactone) copolymer has also been prepared using polystyrene containing a hydroxy chain end as ...
93 citations
TL;DR: The utility of oxidative cyclization reactions for the construction of tetrahydrofuran rings has been examined and alcohol nucleophiles were found to be effective traps for radical cation intermediates generated from both enol ether and ketene dithioacetal groups.
Abstract: The utility of oxidative cyclization reactions for the construction of tetrahydrofuran rings has been examined. In these experiments, alcohol nucleophiles were found to be effective traps for radical cation intermediates generated from both enol ether and ketene dithioacetal groups. The reactivity of the alcohol trapping group appeared to lie between that of an enol ether and an allylsilane trapping group. The stereochemical outcome of cyclization reactions originating from the oxidation of an enol ether was found to be controlled by stereoelectronic factors. The utility of these cyclization reactions was illustrated with the synthesis of a key tetrahydrofuran building block for the synthesis of linalool oxide and rotundisine. Cyclization reactions triggered by the oxidation of a ketene dithioacetal led to far greater levels of stereoselectivity. The stereochemical outcome of these reactions was shown to arise from steric factors involving the larger ketene acetal group. The synthetic utility of cyclizations utilizing ketene dithioacetal derived radical cations was demonstrated by completing an asymmetric synthesis of (+)-nemorensic acid. Finally, the reactions were shown to be compatible with the use of an amide nucleophile and the direct formation of a lactone product.
86 citations
TL;DR: The noncatalytic destructive adsorption of 2-chloroethyl)ethyl sulfide (2-CEES) on nanocrystalline magnesium oxide (MgO) was studied in several solvents from pentane to methanol as mentioned in this paper.
Abstract: The noncatalytic destructive adsorption of (2-chloroethyl)ethyl sulfide (2-CEES), a mimic of bis(2-chloroethyl) sulfide (“HD” or Mustard Gas), on nanocrystalline magnesium oxide (AP-MgO) was studied in several solvents from pentane to methanol. The decomposition products formed in these reactions were vinylethyl sulfide and (2-hydroxyethyl)ethyl sulfide. Reactions in pentane allowed the highest reaction rates, while tetrahydrofuran (THF) and methanol gave results quite different from those for the hydrocarbon solvent. Reactions in methanol yielded (methoxyethyl)ethyl sulfide and not the vinylethyl sulfide and (2-hydroxyethyl)ethyl sulfide compounds. These studies showed that the MgO-2-CEES reaction chemistry is significantly affected by the solvent present and can be enhanced by choice of solvent and the addition of small amounts of water. Interestingly, the least polar, least reactive solvent (pentane) allowed the most rapid 2-CEES reactions, indicating that the solvent simply aided material transfer to ...
TL;DR: Azo compounds, both symmetric and unsymmetric, are cleaved to amine(s) by using commercial zinc dust and ammonium formate or formic acid in methanol, tetrahydrofuran or dioxane at room temperature.
TL;DR: The polyimides ABTP/6FDA (2c) and ABTT/6 FDA (3c) showed very high thermal stability even up to 532 °C for 5% weight loss in synthetic air and glass transition temperature up to 287 °C (by DSC) in nitrogen.
Abstract: Novel diamine monomers, 2,6-bis(3'-trifluoromethyl-p-aminobiphenyl ether)pyridine (TABP) and 2,5- bis(3'-trifluoromethyl-p-aminobiphenyl ether)thiophene (TABT) have been synthesized, which lead to a number of novel fluorinated polyimides by thermal imidization routes when reacted with different commercially available dianhydrides like pyromellitic dianhydride (PMDA), benzophenone tetracarboxylic acid dianhydride (BTDA) or 2,2-bis(3,4- dicarboxyphenyl) hexafluoropropane (6FDA). The polyimides ABTP/6FDA and ABTT/6FDA are soluble in several organic solvents such as N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc) and tetrahydrofuran (THF). The polyimide ABTP/PMDA is only soluble in N- methylpyrollidone (NMP) whereas ABTT/PMDA is insoluble in all solvents. The polyimides ABTP/6FDA (2c) and ABTT/6FDA (3c) exhibited number-average molecular weight 32 940 (polydispersity index (PDI), 1.97) and 24 760 (PDI, 1.87) respectively. These polyimide films have low water absorption rate 0.3-0.9% and low dielectric constant 2.92-3.29 at 1 MHz. These polyimides showed very high thermal stability even up to 532 °C for 5% weight loss in synthetic air and glass transition temperature up to 287 °C (by DSC) in nitrogen. All polyimides formed tough transparent films, with tensile strength up to 115 MPa, a modulus of elasticity up to 2.91 GPa and elongation at break up to 12% depending upon the exact repeating unit structure.
TL;DR: Density functional theory calculations indicate that all H(solvent)(2)(+) cations have low barriers to movement of the proton within an interval along the O.H.O trajectory, i.e., they are examples of so-called SSLB H-bonds (short, strong, low-barrier).
Abstract: Large, inert, weakly basic carborane anions of the icosahedral type CHB(11)R(5)X(6)(-) (R = H, Me; X = Cl, Br) allow ready isolation and structural characterization of discrete salts of the solvated proton, [H(solvent)(x)][CHB(11)R(5)X(6)], (solvent = common O-atom donor). These oxonium ion Bronsted acids are convenient reagents for the tuned delivery of protons to organic solvents with a specified number of donor solvent molecules and with acidities leveled to those of the chosen donor solvent. They have greater thermal stability than the popular [H(OEt(2))(2)][BAr(F)] acids based on fluorinated tetraphenylborate counterions because carborane anions can sustain much higher levels of acidity. When organic O-atom donors such as diethyl ether, tetrahydrofuran, benzophenone, and nitrobenzene are involved, the coordination number of the proton (x) in [H(solvent)(x)()](+) is two. A mixed species involving the [H(H(2)O)(diethyl ether)](+) ion has also been isolated. These solid-state structures provide expectations for the predominant molecular structures of solvated protons in solution and take into account that water is an inevitable impurity in organic solvents. The O.O distances are all short, lying within the range from 2.35 to 2.48 A. They are consistent with strong, linear O.H.O hydrogen bonding. Density functional theory calculations indicate that all H(solvent)(2)(+) cations have low barriers to movement of the proton within an interval along the O.H.O trajectory, i.e., they are examples of so-called SSLB H-bonds (short, strong, low-barrier). Unusually broadened IR bands, diagnostic of SSLB H-bonds, are observed in these H(solvent)(2)(+) cations.
TL;DR: This investigation revealed that the above bond construction was not feasible due to the decomposition of metalloeneamine III under the reaction conditions, and the objective in the present communication is the synthesis of the subunits IV and V by a revised fragment coupling strategy, where epoxide alkylation precedes diene formation (transform T2).
Abstract: In the preceding communication,[1] the proposed synthesis plan identified the two principal pectenotoxin-4 subunits II and III (Figure 1). It was our intention to couple these fragments through the alkylation of the metalloenamine derived from hydrazone III, readily available from the coupling of advanced intermediates IV and V (transform T2), by epoxide II. However, this investigation revealed that the above bond construction was not feasible due to the decomposition of metalloeneamine III under the reaction conditions.[2] Accordingly, the objective in the present communication is the synthesis of the subunits IV and V, and the completion of the syntheses of pectenotoxin-4 (1) and pectenotoxin-8 by a revised fragment coupling strategy, where epoxide alkylation (transform T1) precedes diene formation (transform T2). The plan for the construction of the F-ring tetrahydrofuran IV was to involve a C37 hydroxy-directed epoxidation of olefin VI with a subsequent ring closure by the C32 hydroxy moiety (transform T3). Finally, the stereoselective formation of the E-ring tetrahydrofuran V from its acyclic precursor VII was based on an iodoetherification precedent provided by Bartlett and Rychnovsky (transform T4). The synthesis of the ring-E synthon V began with the known aldol adduct adduct 2 (Scheme 1).[4] Reduction of 2 (LiBH4, THF, 0 8C), and selective protection of the primary alcohol (TBSCl, Im, CH2Cl2, 100% over two steps) afforded allylic alcohol 3.[5] Acylation of 3 with the PMB-protected lactic acid 4[6] (DCC, DMAP, CH2Cl2, 52%), followed by carbonyl olefination of 5a with Tebbe reagent[7] afforded the 1,5-diene 5b. Claisen rearrangement of 5b in refluxing toluene gave the desired rearrangement product 6 in 82% yield for the two steps. Chelate-controlled reduction of the resulting ketone (Zn(BH4)2, Et2O, 78 8C, 86%, d.r. 86:14) provided the precursor for the key iodoetherification reaction. In spite of the modest selectivity that was observed for the formation of the desired tetrahydrofuran 7 (NIS, CH3CN, 40 8C, 89%, d.r. 72:28), this outcome proved sufficient to pursue the planned route. Successive radical dehalogenation of 7 (Bu3SnH, AIBN, toluene, 100%) and deprotection of the primary TBS ether (TBAF, THF, 95%) afforded alcohol 8. Oxidation with Dess± Martin reagent[8] (py, CH2Cl2, 99%), Wittig homologation (EtOC(O)CC(CH3)PPh3, THF, 65 8C; 100% E :Z> 95:5), and ester reduction (LiAlH4, Et2O, 0 8C, 92%) completed the carbon assembly of the E-ring fragment. Benzyl protection (NaH, BnBr, TBAI, THF/DMF, 94%) followed by PMB deprotection (DDQ, CH2Cl2/pH 7 buffer, 95%) gave alcohol 10. Oxidation to the methyl ketone[8] (Dess±Martin periodinane, py, CH2Cl2, 93%), and hydrazone formation (TMSCl, CH2Cl2/Me2NNH2, 100%) completed the synthesis of hydrazone 11. As summarized in Figure 1, the first stage of the synthesis of the ring-F fragment IV will be simplified to the construction of the C31±C35 phosphonium salt, the C36±C40 aldehyde, and their union through a Wittig coupling to afford the Zolefin VI. The synthesis of the C31±C35 phosphonium salt began with the known triol derivative 12 (Scheme 2).[9] Protection of the hydroxy group at C33 of 12 as a PMB ether (PMBBr, NaH, THF/DMF, 95%) followed by reductive ozonolysis (O3, EtOH, then DMS, then NaBH4, 95%) afforded alcohol 13. Transformation of 13 to the corresponding iodide (I2, Im, Ph3P, CH2Cl2, 0 8C, 89%) proceeded smoothly, but careful control of the temperature was required to access phosphonium salt 14 (Ph3P, CH3CN, 55 8C, 89%).[10] The synthesis of the aldehyde partner 17 began with protection of the hydroxy group at C37 of aldol adduct 15[11] as a base-sensitive triphenylsilyl ether (TPSCl, Im, DMAP, DMF, 0 8C, 98%; Scheme 2). Half reduction of the S-phenyl thioester[12] (Pd/C, Et3SiH, acetone, 95%), and olefination under modified Lombardo conditions[13] ([Cp2ZrCl2], Zn dust, CH2I2, THF, 0 8C, 84%) afforded olefin 16. RhodiumCOMMUNICATIONS
TL;DR: In this article, a complex parallel ECE mechanism is proposed, comprising the loss of the SCN ligands in their pristine (anionic) form, which is initiated by the metal-centered oxidation process.
Abstract: The redox properties of cis-[Ru(dcbpyH2)2(NCS)2] ([Ru(dcbpyH2)2(NCS)2]; dcbpyH2 = 2,2‘-bipyridine- 4,4‘-dicarboxylic acid) have been investigated in various solvents by combining electrochemical techniques (cyclic voltammetry (CV) and spectroelectrochemistry), mass spectrometry, digital simulation techniques, and semiempirical quantum chemical calculations. The electrochemical study has shown that while in polar solvents such as acetonitrile and ethanol the complex undergoes, following oxidation, the rapid loss of SCN ligands, forming the corresponding solvato complexes. In the less polar solvent tetrahydrofuran, a reversible oxidative CV behavior is observed at relatively low scan rates. On the basis of the CV and spectroelectrochemical studies and supported by quantum chemical calculations, a complex parallel ECE mechanism is proposed, comprising the loss of the SCN ligands in their pristine (anionic) form, which is initiated by the metal-centered oxidation process.
TL;DR: A crown ether derivative (4′-allyldibenzo-18-crown-6, CE) was covalently incorporated into the network of temperature sensitive poly(N-isopropylacrylamide) (PNIPA) hydrogels by copolymerization in a mixed solvent of water and tetrahydrofuran (H2O/THF) as discussed by the authors.
TL;DR: In this article, the preparation of 2,4-disubstituted imidazoles from the condensation of α-haloketones with amidines is described.
TL;DR: A change in stereoselectivity between solutions in DEE and THF was found to be general among a number of different chiral lithium amides, all with an internal chelating methoxy group.
Abstract: Lithioacetonitrile and a chiral lithium amide with an internally coordinating methoxy group form mixed dimers in diethyl ether (DEE) and in tetrahydrofuran (THF) according to NMR studies. Based on the observed 6 Li, 1 H heteronuclear Overhauser effects, in THF lithioacetonitrile is present in a mixed complex with the chiral lithium amide, and this complex has a central N-Li-N-Li core. In DEE, on the other hand, the acetonitrile anion bridges two lithiums of the dimer to form a central six-membered Li-N-C-C-Li-N ring. Gauge individual atomic orbital DFT calculations of the 1 3 C NMR chemical shifts of the DEE-and THF-solvated mixed dimers show good agreement with those obtained experimentally. Lithioacetonitrile complexed to the chiral lithium amide has been employed in asymmetric addition to benzaldehyde in both DEE and THF. In THF the product, (S)-3-phenyl-3-hydroxy propionitrile, is formed in 55% ee and in DEE the R enantiomer is formed in 45% ee. This change in stereoselectivity between solutions in DEE and THF was found to be general among a number of different chiral lithium amides, all with an internal chelating methoxy group.
TL;DR: In this paper, a self-polyaddition of 4-hydroxybutyl vinyl ether with a hydroxyl group was performed to obtain polyacetals of the structure [CH(CH3)OCH2CH2 CH2CH 2CH2O]n quantitatively.
Abstract: To establish the optimum conditions for obtaining high molecular weight polyacetals by the self-polyaddition of vinyl ethers with a hydroxyl group, we performed the polymerization of 4-hydroxybutyl vinyl ether (CH2CHOCH2CH2CH2CH2OH) with various acidic catalysts [p-toluene sulfonic acid monohydrate, p-toluene sulfonic anhydride (TSAA), pyridinium p-toluene sulfonate, HCl, and BF3OEt2] in different solvents (tetrahydrofuran and toluene) at 0 °C. All the polymerizations proceeded exclusively via the polyaddition mechanism to give polyacetals of the structure [CH(CH3)OCH2CH2CH2CH2O]n quantitatively. The reaction with TSAA in tetrahydrofuran led to the highest molecular weight polymers (number-average molecular weight = 110,000, weight-average molecular weight/number-average molecular weight = 1.59). 2-Hydroxyethyl vinyl ether, diethylene glycol monovinyl ether, cyclohexane dimethanol monovinyl ether, and tricyclodecane dimethanol monovinyl ether were also employed as monomers, and polyacetals with various main-chain structures were obtained. This structural variety of the main chain changed the glass-transition temperature of the polyacetals from approximately −70 °C to room temperature. These polyacetals were thermally stable but exhibited smooth degradation with a treatment of aqueous acid to give the corresponding diol compounds in quantitative yields. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4053–4064, 2002
TL;DR: In this paper, a general one-pot, purification-free synthesis of diethyl N-Boc-1-aminoalkylphosphonates has been developed.
TL;DR: Carbonyl ylides react with tetraarylporphyrins to afford the corresponding [3+2] tetrahydrofuran cycloaddition products in moderate yields.
TL;DR: In this paper, the preferential solvation of N-ethyl-4-cyanopyridinium iodide and 2,6-diphenyl-4(2,4-6-triphenyl -1-pyridino)-phenolate [Reichardt's E T (30) dye] has been studied in ethanol + tetrahydrofuran, ethanol + acetonitrile, ethanol+ acetoni-leitrile and acetonititrile + tetrahedraide-based mixtures as a
Abstract: Preferential solvation of N-ethyl-4-cyanopyridinium iodide and 2,6-diphenyl-4(2,4,6-triphenyl-1-pyridino)-phenolate [Reichardt's E T (30) dye] has been studied in ethanol + tetrahydrofuran, ethanol + acetonitrile and acetonitrile + tetrahydrofuran binary mixtures as a function of temperature and composition of mixed binary solvents. It has been found that besides solute-solvent interaction, solvent-solvent interaction plays an important role in determining the solvation characteristics.
TL;DR: A series of substituted-phenyl p -dimethylaminobenzoates with para-or meta-substitution at the ester phenyl ring (p -OH, p -CH 3, H, p-Br, m -Cl, and p -NO 2 ) were synthesized and their fluorescence spectra were recorded in polar solvents as discussed by the authors.
TL;DR: In this paper, the reaction of O-pentafluorobenzoyloximes of olefinic ketones with a catalytic amount of Pd(PPh 3 ) 4 and triethylamine in dimethylformamide (DMF) affords nitrogen-containing heterocycles, such as pyrroles, pyridines, isoquinolines, spiro-imines, and aza-azulenes.
Abstract: Electrophilic amination of Grignard reagents is accomplished by using O-sulfonyl- oximes of benzophenone derivatives. In the presence of a catalytic amount of CuCN, O-sul- fonyloxime of 4,4'-bis(trifluoromethyl)benzophenone reacts with alkyl Grignard reagents in tetrahydrofuran (THF) and hexamethylphosphoramide (HMPA), yielding primary alkyl- amines by successive hydrolysis of the resulting N-alkylimines. Arylamines are also prepared as well as alkylamines by treating O-sulfonyloxime of 3,3',5,5'-tetrakis(trifluoromethyl)- benzophenone in toluene-ether with Grignard reagents. Various cyclic imines are synthesized by palladium-catalyzed cyclization of olefinic oxime derivatives. That is, the reaction of O-pentafluorobenzoyloximes of olefinic ketones with a catalytic amount of Pd(PPh 3 ) 4 and triethylamine in dimethylformamide (DMF) affords nitrogen-containing heterocycles, such as pyrroles, pyridines, isoquinolines, spiro- imines, and aza-azulenes. This reaction proceeds via the initial formation of alkylidene- aminopalladium species generated by oxidative addition of oximes to Pd(0), and the succes- sive intramolecular Heck-type amination occurs on the olefinic moiety.
TL;DR: In this paper, carbon-carbon bonding forming reactions of two cyclic sulfate esters and an organocuprate species are reported, the former with lithium dianions to give substituted tetrahydrofuran derivatives with displacement of sulfate.
TL;DR: In this article, it was shown that the sodium siloxides (tBu3SiONa)4 and tBu2PhSiONaa)4 can be synthesized almost quantitatively from the reaction of the sodium-siloxides tBu 3SiNa and tbu 2PhSiNa with N2O in tetrahydrofuran at −78 °C.
TL;DR: A remarkably versatile synthesis of cis-stilbenoid hydrocarbons containing highly functionalized phenyl groups is developed via an efficient palladium-catalyzed coupling of aryl Grignard reagents with trans-1,2-dibromoalkenes in tetrahydrofuran.
Abstract: A remarkably versatile synthesis of cis-stilbenoid hydrocarbons containing highly functionalized phenyl groups is developed via an efficient palladium-catalyzed coupling of aryl Grignard reagents with trans-1,2-dibromoalkenes (generally obtained via bromination of the corresponding dialkylacetylenes) in tetrahydrofuran.
TL;DR: In this article, a pendent bis(ether anhydride), 1, 1-bis[4-dicarboxyphenoxy)phenyl]-4-phenylcyclohexane dianhydride, was prepared in three steps, starting from the nitrodisplacement of 1,1-bis(4-hydroxyphenyl)-4-hexane with 4-nitrophthalonitrile, followed by alkaline hydrolysis of the bis (ether dinitrile) and subsequent dehydration of the resulting bis( ether di
Abstract: A new bulky pendent bis(ether anhydride), 1,1-bis[4-(4-dicarboxyphenoxy)phenyl]-4-phenylcyclohexane dianhydride, was prepared in three steps, starting from the nitrodisplacement of 1,1-bis(4-hydroxyphenyl)-4-phenylcyclohexane with 4-nitrophthalonitrile to form bis(ether dinitrile), followed by alkaline hydrolysis of the bis(ether dinitrile) and subsequent dehydration of the resulting bis(ether diacid). A series of new poly(ether imide)s were prepared from the bis(ether anhydride) with various diamines by a conventional two-stage synthesis including polyaddition and subsequent chemical cyclodehydration. The resulting poly(ether imide)s had inherent viscosities of 0.50–0.73 dL g−1. The gel permeation chromatography measurements revealed that the polymers had number-average and weight-average molecular weights of up to 57,000 and 130,000, respectively. All the polymers showed typical amorphous diffraction patterns. All of the poly(ether imide)s showed excellent solubility in comparison with the other polyimides derived from adamantane, norbornane, cyclododecane, and methanohexahydroindane and were readily dissolved in various solvents such as N-methyl-2-pyrrolidinone, N,N-dimethylacetamide (DMAc), N,N-dimethylformamide, pyridine, cyclohexanone, tetrahydrofuran, and even chloroform. These polymers had glass-transition temperatures of 226–255 °C. Most of the polymers could be dissolved in chloroform in as high as a 30 wt % concentration. Thermogravimetric analysis showed that all polymers were stable up to 450 °C, with 10% weight losses recorded from 458 to 497 °C in nitrogen. These transparent, tough, and flexible polymer films could be obtained by solution casting from DMAc solutions. These polymer films had tensile strengths of 79–103 MPa and tensile moduli of 1.5–2.1 GPa. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2066–2074, 2002
TL;DR: In this article, the NMR and crystallographic characterization of lithium bis[salicylato(2-)]borate, Li(BSB), and lithium bis [1,2-benzenediolato (2-)-O,O']borate Li(BBB), are reported.
Abstract: The NMR and crystallographic characterization of lithium bis[salicylato(2-)]borate, Li(BSB), and lithium bis[1,2-benzenediolato(2-)-O,O‘]borate, Li(BBB), are reported. The single-strand polymer {(MeCN)2 Li(BSB)}∞ crystallizes from a saturated solution of Li(BSB) in ethanenitrile and consists of μ2-{(MeCN)2Li}+ cations bridging the exocyclic oxygen atoms of two [BSB]- anions. Crystallization of Li(BSB) from tetrahydrofuran produces {(THF)2Li(BSB)}∞, which has essentially the same structure as {(MeCN)2Li(BSB)}∞. In contrast, crystals of Li(BBB) grown from THF/diethyl ether or THF/toluene mixtures (1:1) contain adventitious water and form a hydrogen-bonded, three-dimensional lattice comprising {(H2O)2(THF)Li(BBB)} units. This novel structural motif contains the first example of lithium bound to one THF and two water molecules, and also exhibits hydrogen bonding between the water and the THF. Ab initio calculations suggest that the Li−OBBB bond in {(H2O)2(THF)Li(BBB)}∞, while still predominantly ionic in char...