Showing papers on "Ether published in 1997"
TL;DR: Several propane-oxidizing bacteria were tested for their ability to degrade gasoline oxygenates, including methyl tert-butyl ether (MTBE), ethyl tert- butyl Ether (ETBE), and tert-amyl methyl ether (TAME), and both a laboratory strain and natural isolates were able to degrade each compound after growth on propane.
Abstract: Several propane-oxidizing bacteria were tested for their ability to degrade gasoline oxygenates, including methyl tert-butyl ether (MTBE), ethyl tert-butyl ether (ETBE), and tert-amyl methyl ether (TAME). Both a laboratory strain and natural isolates were able to degrade each compound after growth on propane. When propane-grown strain ENV425 was incubated with 20 mg of uniformly labeled [14C]MTBE per liter, the strain converted > 60% of the added MTBE to 14CO2 in < 30 h. The initial oxidation of MTBE and ETBE resulted in the production of nearly stoichiometric amounts of tert-butyl alcohol (TBA), while the initial oxidation of TAME resulted in the production of tert-amyl alcohol. The methoxy methyl group of MTBE was oxidized to formaldehyde and ultimately to CO2. TBA was further oxidized to 2-methyl-2-hydroxy-1-propanol and then 2-hydroxy isobutyric acid; however, neither of these degradation products was an effective growth substrate for the propane oxidizers. Analysis of cell extracts of ENV425 and experiments with enzyme inhibitors implicated a soluble P-450 enzyme in the oxidation of both MTBE and TBA. MTBE was oxidized to TBA by camphor-grown Pseudomonas putida CAM, which produces the well-characterized P-450cam, but not by Rhodococcus rhodochrous 116, which produces two P-450 enzymes. Rates of MTBE degradation by propane-oxidizing strains ranged from 3.9 to 9.2 nmol/min/mg of cell protein at 28 degrees C, whereas TBA was oxidized at a rate of only 1.8 to 2.4 nmol/min/mg of cell protein at the same temperature.
364 citations
TL;DR: A new method for selective and efficient cleavage of arylglycerol−β-aryl (β-O-4) ether linkages in lignins is introduced and the acronym “DFRC” relates to the reactions involved, derivatization followed by reductive cleavage.
Abstract: A new method for selective and efficient cleavage of arylglycerol−β-aryl (β-O-4) ether linkages in lignins is introduced. The acronym “DFRC” relates to the reactions involved, derivatization followed by reductive cleavage. Derivatization, accompanied by cell wall solubilization, is accomplished with acetyl bromide in acetic acid; reductive cleavage of resulting β-bromo ethers utilizes zinc in an acidic medium. Following acetylation, degradation monomers (4-acetoxycinnamyl acetates) are quantified by GC, providing data analogous to those from analytical thioacidolysis. Keywords: Acetyl bromide; lignin; β-aryl ether; thioacidolysis; reductive elimination
287 citations
TL;DR: In this paper, a new method for selective and efficient cleavage of arylglycerol-β-aryl (β-O-4) ether linkages in lignins is described and applied to several lignin β-ether models.
Abstract: A new method for selective and efficient cleavage of arylglycerol-β-aryl (β-O-4) ether linkages in lignins is described and applied to several lignin β-ether models. The term “DFRC” was coined for derivatization followed by reductive cleavage. Derivatization, accompanied by cell wall solubilization, is accomplished with acetyl bromide (AcBr); reductive cleavage of resulting β-bromo ethers utilizes zinc in acetic acid. Degradation monomers, 4-acetoxycinnamyl acetates, from β-ether cleavage by the DFRC method were identified by NMR, GC−MS, and comparison of GC retention times with authentic compounds. Under the conditions used in this study, the β-ether linkage of all models was cleaved in very high (>92%) yield. The DFRC method produces simpler mixtures of monomers with higher yields than alternative hydrolytic methods. Because of its relative simplicity, mild conditions, and exceptional selectivity, this method should become a powerful analytical method for lignin characterization. Keywords: Acetyl bromid...
180 citations
TL;DR: The photooxidation mechanism of the polyether segment was studied using the photodecomposition of polytetramethylene glycol, PTMG, as a model for that of the soft segments of ETHDI as discussed by the authors.
173 citations
TL;DR: In this paper, a distributed multipole analysis (DMA)-based description of the electrostatic energy, and intermolecular perturbation theory (IMPT) calculations, hydrogen bonding between donor alkanol hydroxyl groups and oxygen acceptor atoms in ketone, ether, and ester functional groups is characterized.
Abstract: An attractive way to study intermolecular hydrogen bonding is to combine analysis of experimental crystallographic data with ab initio—based energy calculations. Using the Cambridge Structural Database (CSD), a distributed multipole analysis (DMA)-based description of the electrostatic energy, and intermolecular perturbation theory (IMPT) calculations, hydrogen bonding between donor alkanol hydroxyl groups and oxygen acceptor atoms in ketone, ether, and ester functional groups is characterized. The presence and absence of lone pair directionality to carbonyl and ether or ester oxygens, respectively, can be explained in terms of favored electrostatic energies, the major attractive contribution in hydrogen bonding. A hydrogen bond in its optimum geometry is only slightly stronger when formed to a ketone group than to an ether group. Hydrogen bonds formed to carbonyl groups have similar properties in a ketone or ester, but the ester O2 differs from an ether oxygen due to various environmental effects rather than a change in its intrinsic properties. For (E)-ester oxygens, there are few hydrogen bonds found in the CSD because of the competition with the adjacent carbonyl group, but the interaction energies are similar to an ether. Hydrogen bonds to O2 of (Z)-esters are destabilized by the repulsive electrostatic interaction with the carbonyl group. The relative abundance of nonlinear hydrogen bonds found in the CSD can be explained by geometrical factors, and is also due to environmental effects producing slightly stronger intermolecular interaction energies for an off-linear geometry. © 1997 by John Wiley & Sons, Inc. J Comput Chem 18: 757–774, 1997
172 citations
TL;DR: In this paper, cloud-point curves by DSC measurements at different scanning rates on solutions of two samples of poly(vinyl methyl ether) in water show two minima in a temperature-composition plot.
Abstract: Cloud-point curves by DSC measurements at different scanning rates on solutions of two samples of poly(vinyl methyl ether) in water show two minima in a temperature−composition plot. The significance of the data was confirmed by static measurements of the coexisting-phase compositions and phase-volume ratios. A thermodynamic analysis in terms of a strongly concentration-dependent interaction parameter leads to the conclusion that the system H2O/PVME exhibits so-called type III behavior. For polymers of infinite molar mass, such behavior is characterized by the occurrence of two off-zero critical concentrations, in addition to the usual zero critical concentration marking the ϑ state.
157 citations
TL;DR: Evidence for two novel metabolic processes catalyzed by a filamentous fungus, Graphium sp.
Abstract: In this study, evidence for two novel metabolic processes catalyzed by a filamentous fungus, Graphium sp. strain ATCC 58400, is presented. First, our results indicate that this Graphium sp. can utilize the widely used solvent diethyl ether (DEE) as the sole source of carbon and energy for growth. The kinetics of biomass accumulation and DEE consumption closely followed each other, and the molar growth yield on DEE was indistinguishable from that with n-butane. n-Butane-grown mycelia also immediately oxidized DEE without the extracellular accumulation of organic oxidation products. This suggests a common pathway for the oxidation of both compounds. Acetylene, ethylene, and other unsaturated gaseous hydrocarbons completely inhibited the growth of this Graphium sp. on DEE and DEE oxidation by n-butane-grown mycelia. Second, our results indicate that gaseous n-alkane-grown Graphium mycelia can cometabolically degrade the gasoline oxygenate methyl tert-butyl ether (MTBE). The degradation of MTBE was also completely inhibited by acetylene, ethylene, and other unsaturated hydrocarbons and was strongly influenced by n-butane. Two products of MTBE degradation, tert-butyl formate (TBF) and tert-butyl alcohol (TBA), were detected. The kinetics of product formation suggest that TBF production temporally precedes TBA accumulation and that TBF is hydrolyzed both biotically and abiotically to yield TBA. Extracellular accumulation of TBA accounted for only a maximum of 25% of the total MTBE consumed. Our results suggest that both DEE oxidation and MTBE oxidation are initiated by cytochrome P-450-catalyzed reactions which lead to scission of the ether bonds in these compounds. Our findings also suggest a potential role for gaseous n-alkane-oxidizing fungi in the remediation of MTBE contamination.
151 citations
TL;DR: In this article, Rubbery polymers with a high H2S/CH4 selectivity were synthesized and cast in the form of "dense" (homogeneous) membranes.
145 citations
TL;DR: In this article, a zeolite membrane grown hydrothermally on the surface of a porous gelatin substrate showed a high alcohol selectivity in pervaporation, a membrane-based liquid separation process, of alcohol-benzene, cyclohexane or methyl tert-butyl ether.
138 citations
TL;DR: Cationic ring-opening polymerization of cyclic carbonates with alkyl halide as initiator during which no decarboxylation takes place is described in detail as mentioned in this paper.
Abstract: Cationic ring-opening polymerization of cyclic carbonates with alkyl halide as initiator during which no decarboxylation takes place is described in detail, using 5,5-dimethyl-1,3-dioxan-2-one (1), 1,3-dioxan-2-one (2), 5-n-butyl-1,3-dioxan-2-one (5), and 1,3-dioxaspiro[5.5]undecan-2-one (6) as monomers. Cationic polymerizations of 2, 5, and 6 with cationic initiators such as methyl triflate and boron trifluoride etherate were carried out under various conditions. In the polymerizations decarboxylation (elimination of carbon dioxide) during the polymerization occurred to yield the corresponding polycarbonate with ether units (5−10%) in the main chain. 6 only gave a small amount of polymer. Prolonged reaction time and enhanced temperature accelerated the decarboxylation. Reactions of the polycarbonate of 2 with several cationic initiators including methyl iodide were monitored by 1H NMR and gel permeation chromatography. Both a decrease in the polymer molecular weight and an increase in the ratio of ether ...
126 citations
TL;DR: In this paper, a sardine oil system was used to determine the relationship between molecular structure and the antioxidant activity (AA) of various compounds, representative of the major functional groups in phospholipids.
Abstract: Various compounds, representative of the major functional groups in phospholipids, phosphatidylethanolamine and phosphatidylcholine, were tested for antioxidant activity (AA) in a sardine oil system to determine the relationship between molecular structure and the AA of these compounds. AA was found to be attributable not only to the side-chain amino groups but also to the cooperative effect of the hydroxy group in the side chain. Choline and ethanolamine, side-chain moieties of phospholipids, strongly inhibited increases in peroxide values in a sardine oil mixture during storage; however, phosphatidic acid derivatives and glycerol, also major functional groups of phospholipids, did not show AA. Choline and ethanolamine have hydroxy amines as functional groups; therefore, several model reagents that contained amines and alcohols were assayed to compare the activity of the amino group with that of the hydroxy group. All basic alkylamines examined had AA as decomposers of hydroperoxides. The intramolecular hydroxy group in these amines complemented AA of the amino group. Only intramolecular alcohol, which can donate a proton, showed strong synergistic activity with AAof the basic amines, while protected groups, such as methyl ether and phosphate ester, did not show this effect.
TL;DR: The cross-linked HA film with a water content of 60 wt% exhibited practically no weight loss after 10 days of immersion in phosphate-buffered saline (pH 7.4), while this film underwent in vivo degradation by 30% weight Loss after 7 days of subcutaneous implantation in rats.
TL;DR: The reaction of 2 equiv of lithium 1-phenylboratabenzene with ZrCl4 in ether with C2H4 was studied in a single-crystal X-ray diffraction study as mentioned in this paper.
TL;DR: In this paper, a self-assembly of tetranuclear macrocycles via selfassembly that combine crown ether and calixarene chemistry with molecular squares was employed to characterize these unique supramolecular species.
Abstract: Reaction of metallacrown and metallacalixarene platinum bistriflates with bipyridine as well as other bidentate connector ligands results in the formation of tetranuclear macrocycles via self-assembly that combine crown ether and calixarene chemistry with molecular squares Multinuclear NMR spectroscopy and electrospray mass spectrometry are employed to characterize these unique supramolecular species The calixarene metallamacrocycles are used in simple transport experiments to carry sulfonate salts from one aqueous phase into another through chloroform
TL;DR: The results of the structure-activity relationship analysis indicate that in highly active compounds the two aryl rings in the hydrophobic moiety deviate from a common plane, so they are capable of interacting with hydrogen bond donors of P-170 glycoprotein (P-gp) via pi-hydrogen-pi interactions.
Abstract: The effect of 24 newly synthesized quinoline derivatives on tumor cell multidrug resistance (MDR) was examined in vitro. At low concentrations, these compounds enhanced the accumulation of [3H]vincristine in K562/ADM cells and reversed tumor cell MDR. The results of the structure−activity relationship analysis indicate that in highly active compounds the two aryl rings in the hydrophobic moiety deviate from a common plane, so they are capable of interacting with hydrogen bond donors of P-170 glycoprotein (P-gp) via π−hydrogen−π interactions. Other major structural features which influence the MDR-reversing activities of these compounds are a quinoline nitrogen atom and a basic nitrogen atom in piperazine. Furthermore, in highly active compounds, the distance between the hydrophobic moiety and the basic nitrogen atom (an atom connected to 2-hydroxypropoxyquinoline) must be at least 5 A. Several compounds were found to reverse vincristine resistance in K562/ADM cells in vitro, and compound 16 (MS-209) was s...
TL;DR: In this article, the trifunctional ligands (R)-1-(diphenylphosphino)-2-((1R,2S,5R)-menthoxy)1-(2-pyridyl)ethane (2R), (S)-1-diphexylphphosphine (2-DPHP), and (S)(phenyl(2-anisyl)phosphinos)(2pyride)methane(3) have been synthesized, as well as the corresponding RuCl
TL;DR: In this article, the photochemical behavior of lignin models in the presence of singlet oxygen was studied and it was shown that, when the phenoxy part of the molecule shows a lower reactivity towards singlet oxidization, the oxidation of the phenol moiety to hydroquinone can occur.
TL;DR: In this paper, an analytical method is described that can detect the major alkyl ether compounds that are used as gasoline oxygenates (methyl tert-butyl ether, MTBE, ETBE, and tert-amyl methyl ether, TAME) in water at sub-ppb concentrations.
Abstract: An analytical method is described that can detect the major alkyl ether compounds that are used as gasoline oxygenates (methyl tert-butyl ether, MTBE; ethyl tert-butyl ether, ETBE; and tert-amyl methyl ether, TAME) and their most characteristic degradation products (tert-butyl alcohol, TBA; tert-butyl formate, TBF; and tert-amyl alcohol, TAA) in water at sub-ppb concentrations. The new method involves gas chromatography (GC) with direct aqueous injec tion (DAI) onto a polar column via a splitless injector, coupled with detection by mass spectrometry (MS). DAI-GC/MS gives excellent agreement with conventional purge-and-trap methods for MTBE over a wide range of environmentally relevant concentrations. The new method can also give simultaneous identification of polar compounds that might occur as degradation products of gasoline oxygenates, such as TBA, TBF, TAA, methyl acetate, and acetone. When the method was applied to effluent from a column microcosm prepared with core material from an urban site in New...
TL;DR: The cross-coupling reaction between 3-iodoindole 8 and vinylstannane 11b gave the 3-alkenylindole 7, which was converted into the triflate 24 in two steps through an allene-mediated electrocyclic reaction.
Abstract: Total syntheses of carazostatin (1), hyellazole (2a), and carbazoquinocins B-F (3b-f) have been completed. The cross-coupling reaction between 3-iodoindole 8 and vinylstannane 11b gave the 3-alkenylindole 7. Treatment of 7 with ethynylmagnesium bromide, followed by etherification of the resulting alcohol 12 with MOMCl, yielded the 3-alkenyl-2-propargylindole 6. The compound 6 was treated with t-BuOK in t-BuOH at 90 degrees C to obtain the desired carbazoles 4 together with the N-deprotected carbazole 13 through an allene-mediated electrocyclic reaction. The carbazole 13a, derived from 4a or 4c, was converted into the triflate 24 in two steps. The triflate 24 was subjected to the Suzuki cross-coupling reaction with either 9-heptyl-9-BBN or phenylboronic acid in the presence of a palladium catalyst to produce the 1-heptylcarbazole 25a and the 1-phenylcarbazole 25b. Cleavage of the ether bond of 25a yielded carazostatin (1). Cleavage of the ether bond of 25b followed by O-methylation gave hyellazole (2a). Oxidation of carazostatin (1) with benzene seleninic anhydride afforded carbazoquinocin C (3c). In a similar way, carbazoquinocins B and D-F (3b,d-f) were synthesized, respectively.
TL;DR: In this article, the enol ethers of 1,4-diacetylbenzene or 2,7-diefetylnaphthalene with p-benzoquinone are combined to give the corresponding helicenes in low yields and low purities.
Abstract: [5]- and [6]helicenebisquinones can be prepared easily and in quantity by combining enol ethers of 1,4-diacetylbenzene or 2,7-diacetylnaphthalene with p-benzoquinone. Similar diethenyl aromatics that either have no ether functions or have them attached not to the double bonds, but to the aromatic rings, give the corresponding helicenes in only low yields and low purities. [6]Helicenebisquinone 11c is resolved into its enantiomers. An X-ray diffraction analysis of the adduct of one of these enantiomers and l-prolinol shows the absolute stereochemistry of 11c and the regiochemistry with which the amine adds to the quinone.
TL;DR: Bond dissociation energies (BDEs) of K+[O(CH3)2]x, x = 1−4; K +[(CH2OCH3), x = 0 and 1; and K+ [c 2H4O)4] are reported in this paper.
Abstract: Bond dissociation energies (BDEs) of K+[O(CH3)2]x, x = 1−4; K+[(CH2OCH3)2]x, x = 1 and 2; and K+[c-(C2H4O)4] are reported. The BDEs are determined experimentally by analysis of the thresholds for c...
TL;DR: Dehydration of alcohol derivatives 4 followed by demethylation led to hydroxylated stilbene-type structures, such as pinosilvine, resveratrol, or piceatannol, which in some cases can be hydrogenated to give saturated molecules such as combretastanin B-4 tetramethyl ether or chrysotobibenzyl.
Abstract: The reaction of 3,5-dimethoxybenzyl trimethylsilyl ether (3) with different aldehydes (n-PrCHO, n-C11H23CHO, MeCHO, PhCHO) in the presence of lithium powder and a catalytic amount of naphthalene (4 mol %) gave, after hydrolysis, the expected alcohols 4 in moderate yields. The dehydroxylation of these compounds through the corresponding mesylates 5 or directly from benzylic derivatives by catalytic hydrogenation, afforded compounds 6, which are finally demethylated to yield 5-alkyl-3,5-dihydroxyresorcinols, such as olivetol (7a), grevillol (7b), 1,3-dihydroxy-5-propylbenzene (7c), or dihydropinosilvine (7d). Dehydration of alcohol derivatives 4 followed by demethylation led to hydroxylated stilbene-type structures, such as pinosilvine (9d), resveratrol (9e), or piceatannol (9f), which in some cases can be hydrogenated to give saturated molecules such as combretastanin B-4 tetramethyl ether (6f) or chrysotobibenzyl (6g). Finally, when the naphthalene-catalyzed lithiation of compound 3 was performed in the p...
TL;DR: In this paper, the negative neighboring group effect has been quantified kinetically using hydrocarbon monomers containing oxygen and sulfur, and rate constants were determined for the ADMET polymerization of bis(4-pentenyl) ether (3), bis(5-hexenyl)-sulfide (4), and bis(6-hexene)-sulphide (6) using both Schrock's catalyst Mo(CHCMe2Ph)(N-2,6-C6H3-i-Pr2)(OCMe(CF3)2
Abstract: The influence of the negative neighboring group has been quantified kinetically using hydrocarbon monomers containing oxygen and sulfur. Rate constants were determined for the ADMET polymerization of bis(4-pentenyl) ether (3), bis(5-hexenyl) ether (4), bis(4-pentenyl) sulfide (5), and bis(5-hexenyl) sulfide (6) using both Schrock's catalyst Mo(CHCMe2Ph)(N-2,6-C6H3-i-Pr2)(OCMe(CF3)2)2 [Mo] and Grubbs' phenyl version of the ruthenium metathesis catalyst RuCl2(CHPh)(PCy3)2 [Ru]. Both catalysts experience the effect of functional group presence. Further, a pure hydrocarbon version of the negative neighboring group effect has also been demonstrated using the monomer 1,5-hexadiene. In this case, [Mo] catalysis produces linear 1,4-polybutadiene in a reaction that exhibits a typical ADMET rate constant and activation energy. On the other hand, [Ru] catalysis leads principally to the formation of cyclic compounds rather than linear polymers. This change in mechanism for [Ru] catalysis can be attributed to multiple...
Patent•
10 Jul 1997
TL;DR: In this paper, a method for degrading an undesirable ether-based environmental contaminant by contacting the ether with a propane-oxidizing microorganism or with an isopropanoloxidising micro-organism to convert the ether to innocuous compounds which are environmentally acceptable was proposed.
Abstract: A method for degrading an undesirable ether-based environmental contaminant by contacting the ether with a propane-oxidizing microorganism or with an isopropanol-oxidizing microorganism to convert the ether to innocuous compounds which are environmentally acceptable, including treating the ether-based contaminants in situ or removing them from the contaminated site for treatment in a bioreactor, examples of the ether-based contaminants being tertiary butyl ethers of the type utilized as gasoline oxygenates, for example, methyl tert-butyl ether, ethyl tert-butyl ether, and methyl tert-amyl ether, and also ether solvents, for example, tetrahydrofuran, and including also means for monitoring the degradation of methyl tert-butyl ether by evaluating the treated contaminated media for degradative intermediates, for example, tert-butyl alcohol and 2-hydroxy isobutyric acid, and further including contacting the ether with a microorganism that is effective in oxidizing 2-hydroxy-isobutyric acid.
TL;DR: In this article, the synthesis and characterization of poly(ether imide)s with ortho-linked main-chain units based on the bis(ether anhydride)s derived from catechol and 2,3-dihydroxynaphthalene was demonstrated.
Abstract: This paper demonstrates the synthesis and characterization of poly(ether imide)s with ortho-linked main-chain units based on the bis(ether anhydride)s derived from catechol and 2,3-dihydroxynaphthalene. The polymerization was conducted in two steps via the formation of a poly(amic acid) precursor followed by thermal cyclodehydration. The resulting polymers were characterized by inherent viscosity, solubility, film-forming ability, tensile tests, differential scanning calorimetry (DSC), thermogravimetry (TG), and wide-angle X-ray diffraction measurements. Typical poly(ether imide)s were noncrystalline and showed excellent thermal stability. The polymers had glass transition temperatures from 193 to 224 °C and exhibited excellent processability. Many poly(ether imide)s were also soluble in dipolar aprotic solvents and m-cresol.
TL;DR: In this article, a series of novel poly(phthalazinone ether sulfone ketone)s was synthesized from bis(4-fluorophenyl) ketone, bis( 4-chlorophenyl), sulfone, and 4-(4-hydroxybenzyl)-2,3-phthalazein-1-one through nucleophilic substitution polycondensation.
Abstract: A series of novel poly(phthalazinone ether sulfone ketone)s was synthesized from bis(4-fluorophenyl) ketone, bis(4-chlorophenyl)sulfone, and 4-(4-hydroxybenzyl)-2,3-phthalazin-1-one through nucleophilic substitution polycondensation. The synthesized polymers exhibited surprisingly high glass transition temperatures and had excellent thermooxidative properties. The melt viscosities of these synthesized polymers are generally too high to be processed by common processing methods because of their very high glass transition temperatures and amorphous microstructure. An attempt was made to reduce their melt viscosities by solution blending the synthesized polymer with two kinds of oligomers: low molecular weight poly(phthalazinone ether sulfone ketone) and commercial poly(ether sulfone). The results proved that the addition of the oligomers to the polymers led to a marked decrease in melt viscosities. Furthermore, no obvious changes were observed in the thermal and mechanical properties of these blends after oligomer additions. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1425–1432, 1997
TL;DR: The reduction potentials of the group 1 or 2 metal, ammonium, and alkylammonium complexes are significantly anodically shifted with respect to that of the free ligand and the electrochemical properties of the "acyclic" p-tert-butylcalixdiquinones 1, 4, and 8 and their complexes have been studied using cyclic and square wave voltammetric techniques.
Abstract: A new library of ionophoric p-tert-butylcalix[4]diquinones containing ester (1), primary, secondary, and tertiary amide (2-4), and crown ether (5) substituents has been synthesized by treatment of the respective 1,3-bis-substituted p-tert-butylcalix[4]arene with Tl(OCOCF3)3 in trifluoroacetic acid. The structures of the free ligands 1 and 2, a p-tert-butylcalix[4]diquinone bridged at the lower rim by two linked veratrole groups (7), and a previously synthesized p-tert-butylcalix[4]diquinone bis(methyl ether) species (8) have been elucidated by X-ray crystallography. The X-ray crystal structures of 1-Sr(ClO4)2, 1-KClO4, 2-NaClO4, 4-n-BuNH3BF4, 5-NaOCOCF3, and 5-KPF6 demonstrate that these complexes adopt the cone conformation in the solid state. Interestingly, cation-quinone oxygen atom coordination occurs at both the upper and lower rim of 2-NaClO4 and 4-n-BuNH3BF4. Solution coordination properties have been studied by both 1H NMR and UV/vis techniques. The electrochemical properties of the "acyclic" p-tert-butylcalixdiquinones 1, 4, and 8 and their complexes have been studied using cyclic and square wave voltammetric techniques. The reduction potentials of the group 1 or 2 metal, ammonium, and alkylammonium complexes are significantly anodically shifted with respect to that of the free ligand. Addition of cations to electrochemical solutions of a p-tert-butylcalixdiquinone-crown-5 compound (5) caused large anodic shifts (by up to 555 mV in the presence of Ba2+) in a manner similar to that of the acyclic species.
TL;DR: The formation of poly(alkylene sebacate−crown ether pseudorotaxane)s by condensation of linear alkylene diols and Sebacoyl chloride in the presence of crown ethers in the neat state has been studied in this article.
Abstract: The formation of poly(alkylene sebacate−crown ether pseudorotaxane)s by condensation of linear alkylene diols and sebacoyl chloride in the presence of crown ethers in the neat state has been studied. It was found that the average number of crown ether molecules per repeat unit in the polypseudorotaxane was a function of (a) the ring size and (b) the stoichiometric ratio of macrocycle to diol but independent of (i) the equilibration time of the diol and crown ether prior to addition of the diacid chloride, (ii) the length of the diol, and (iii) the temperature of equilibration and polycondensation. All of these observations are consistent with the involvement of hydrogen bonding between the diol and the crown ether as a driving force for threading, except the lack of temperature dependence. Dethreading of the isolated polypseudorotaxanes was shown to be extremely slow. Therefore, it was reasoned that the lack of temperature dependence was due to dethreading during the polymerization, inasmuch as once the e...
TL;DR: In this article, the titanabicycle was treated with 1.1 equiv of i-PrOD and then worked up as usual, obtaining a monodeuterated product 10 with high site selectivity and stereoselectivity.
Abstract: tert-Butyl 2-en-7-ynoate 6 was treated with (η2-propene)Ti(O-i-Pr)2 (3), generated in situ from Ti(O-i-Pr)4 or Ti(O-i-Pr)3Cl and i-PrMgCl, in ether at −50 to −20 °C to afford the product 8 in good yield. The presence of the intermediate titanabicycle 7 was verified by bis-deuterolysis with excess D2O. When the titanabicycle 7 was treated with 1.1 equiv of i-PrOD and then worked up as usual, the monodeuterated product 10 was obtained with high site selectivity and stereoselectivity. Other electrophiles such as aldehydes and ketones also reacted with the titanabicycle in a highly stereoselective manner to give cyclopentanes having a stereo-defined side chain. On the contrary, treatment of the corresponding ethyl ester, ethyl 8-(trimethylsilyl)-(E)-2-octen-7-ynoate (28), with 3 under the same conditions followed by the addition of 1.1 equiv of s-BuOH afforded 2-(trimethylsilyl)-1-bicyclo[3.3.0]octen-3-one (32) in 80% yield. Quenching the same reaction mixture with i-PrOD, EtCHO, and Et2CO in place of s-BuOH ...