Showing papers on "Tetrahydrofuran published in 1985"

A rapid-injection (RI) NMR study of the reactivity of butyllithium aggregates in tetrahydrofuran

Abstract: L'influence de l'agregation sur la reactivite du butyllithium vis-a-vis du benzaldehyde et du cyclopentadiene dans le THF est etudiee a −85°C par la methode RMNIR

Acidity measurements in THF. V: Heteroaromatic compounds containing 5-membered rings

Abstract: The pKa's of 13 heterocyclic aromatic compounds have been measured in tetrahydrofuran (THF) using 13C nmr spectroscopy. The acidifying effect of a nitrogen heteroatom is seen to be quite large (4–6...

FT-IR spectra of vacuum deposited clathrate hydrates of oxirane, H2S, THF, and ethane

Abstract: An ability to prepare clathrate hydrates using low temperature–high vacuum techniques, originally demonstrated for the hydrate of oxirane (Bertie and Devlin), has been extended to include the structure I hydrate of H2S, the mixed structure I hydrate of oxirane and ethane, as well as the structure II simple hydrate of THF and the double hydrates of THF with oxirane and H2S. The crystalline clathrate films (∼6 μ) have been formed either by annealing amorphous host–guest deposits at ∼130 K, epitaxial growth at 110 K (oxirane and mixed ethane–oxirane), or direct deposition at 150 K (THF and its double clathrates). Use of the epitaxial approach at ∼100 K has permitted the formation of the oxirane clathrate hydrate containing intact isolated D2O molecules. This has permitted the FT–IR observation of the ν3–ν1 doublet in the O–D stretching region (2455 and 2380 cm−1 at 100 K) with the values, after correction for Fermi resonance, suggesting a splitting from intramolecular coupling of ∼56 cm−1 (2455 vs 2399 cm−1)...

Photochemistry of the o-nitrobenzyl system in solution: evidence for singlet-state intramolecular hydrogen abstraction

Abstract: Several oxygen-substituted o-nitrobenzylic compounds in THF solution were studied by picosecond transient spectroscopy. The o-quinonoid intermediate resulting from intramolecular H abstraction was observed in those compounds which undergo efficient reaction. In the case of phenyl o-nitrobenzyl ether and p-cyanophenyl o-nitrobenzyl ether, both the triplet excited state and the o-quinonoid were observed at early times. For these two compounds, the o-quinonoid intermediate is formed from the singlet excited state at a rate much faster than triplet decay. 18 references, 4 figures.

Mono-η-cycloheptatrienyltitanium chemistry: synthesis, molecular and electronic structures, and reactivity of the complexes [Ti(η-C7H7)L2X](L = tertiary phosphine, O- or N-donor ligand; X = Cl or alkyl)

Abstract: Bis(η-toluene)titanium reacts with cycloheptatriene in the presence of (AlEtCl2)2, at > 60 °C to form [Ti(η-C7H7)(η-C7H9)] and at room temperature [{Ti(η-C7H7)(thf)(µ-Cl)}2](thf = tetrahydrofuran) is also formed. The crystal structure of the latter has been determined. The dimer reacts with the ligands L2= R2PCH2CH2PR2(R = Me or Ph), trans-1,2-bis(dimethylphosphino)cyclopentane, MeOCH2CH2OMe, 2PMe3 or Me2NCH2CH2NMe2, forming the compounds [Ti(η-C7H7)L2Cl]. Reaction of alkyl Grignard reagents with the appropriate chloroderivatives gives the titanium–alkyls [Ti(η-C7H7)L2R][L2= Me2PCH2CH2PMe2, R = Me or Et; L2=trans-1,2-C5H8(PMe2)2, R = Me]. The crystal structure of [Ti(η-C7H7)(Me2PCH2CH2PMe2)Et] has been determined: there is no evidence for Ti–H–C interactions between the Ti and the hydrogens of the ethyl group. The photoelectron spectra of several Ti(η-C7H7) compounds are discussed in terms of the nature of the Ti(η-C7H7) bonding. It is proposed that the chemistry of the Ti(η-C7H7) system corresponds most closely to a formal description of the η-C7H7 group as having a –3 charge rather than the more conventional description as +1. Homogeneous mixtures of [{Ti(η-C7H7)(thf)(µ-Cl)}2] and aluminium alkyls are shown to catalyse ethylene polymerisation.

Preparation and crystal structure of a two-co-ordinate manganese compound, bis[tris(trimethyl)silylmethyl]manganese

Abstract: The product of the reaction between MnCl2 and tris(trimethylsilyl)methyl-lithium in 1:2 molar ratio in tetrahydrofuran is the monomeric species [Mn{C(SiMe3)3}2], the first two-co-ordinate manganese compound to be characterized.

The synthesis, magnetic, electrochemical, and spectroscopic properties of diruthenium(II,II) tetra-µ-carboxylates and their adducts. X-Ray structures of Ru2(O2CR)4L2(R = Me, L = H2O or tetrahydrofuran; R = Et, L = Me2CO)

Abstract: The interaction of the reduced ‘blue solutions’ of ruthenium chloride in methanol with alkali-metal carboxylates yields the air-sensitive paramagnetic complexes, Ru2(µ-O2CR)4(R = H, Me, CH2Cl, Et, or Ph), that form weakly end-co-ordinated bis adducts, Ru2(µ-O2CR)4L2[L = H2O, MeOH, tetrahydrofuran (thf), Me2CO, or MeCN]. Electrochemical measurements, electronic and i.r. absorption spectra, and magnetic susceptibility data are given. The structures of Ru2(O2CMe)4L2(L = H2O or thf) and Ru2(O2CEt)4(Me2CO)2 have been determined by X-ray crystallography and the well known D4h symmetry of binuclear tetracarboxylates established. The Ru2(O2CR)4 core shows a constant geometry with Ru–Ru = 2.261 ± 0.001 A. The three axial donor ligands show slightly varying Ru ⋯ O distances of 2.335(4), 2.363(5), and 2.391(5)A for water, acetone, and thf respectively.

Process for producing polyether polyol and a product

Abstract: A process for producing a polyether polyol with a content of 0.5 to 99.5% by weight of oxytetramethylene groups derived from tetrahydrofuran by copolymerizing tetrahydrofuran or a mixture of tetrahydrofuran and another cyclic ether copolymerizable therewith with a polyhydric alcohol having two or more hydroxyl groups per one molecule with the use of a heteropoly-acid and/or its salt as a catalyst, which comprises allowing 0.1 to 15 molecules of water per one heteropoly-anion to exist in the catalyst phase. The above-described polyether polyol is an industrially useful polymer which is a starting material for polyurethane to be used for spandex or a synthetic leather, etc.

Applications of potassium-graphite and metals dispersed on graphite in organic synthesis

Abstract: Potassium—graphite (CK), easily prepared by melting potassium over graphite at 150—20O' °C under argon, has been used as heterogeneous reagent in several reactions, including the Birch— type reaction of a,19—unsaturated ketones and carboxylic acids and of Schiff's bases, the reductive cleavage of vinylic and allylic sulfones, the selective alkylation of aliphatic esters, imines and nitriles, and the reductive decyanation of nitriles. Potassium— graphite has also been exploited to prepare active metals, highly dispersed on the graphite surface (Met—Gr), by the reaction with the corresponding metal halides in ethereal solvents. The active metals prepared have found applications in Reformatsky reactions (Zn—Gr), preparations of allylic organometallic species (Zn—Gr, Sn—Gr), reductive coupling of carbonyl compounds (Ti—Gr), debromination (Fe—Gr), vinylic and allylic substitution (Pd—Gr), and hydrogenation reactions (Pd—Gr, Ni—Gr). INTRODUCTION Graphite has a characteristic stacked structure in which the carbon layers are held by weak van der Waals forces. This allows a large, yet increasing number of substances to be intercalated, forming lamellar compounds in which monolayers of the guest species are separated by one, two or more carbon layers (ref. 1). The process is accompanied by a macroscopic swelling, due to the increase of the distance between the carbon layers, as evidenced by X—ray diffraction methods. Some of these graphite compounds have found use as reagents or catalysts (ref. 2). Among the lamellar compounds of the alkali metals, potassium—graphite having the composition C8K is the most easy and convenient to prepare by directly melting potassium over graphite at 150—200 °C under argon. Potassium—graphite is a bronze— colored powder constituted by layers of potassium ions alternating with negatively charged carbon layers (Fig. 1). Potassium—graphite is pyrophoric and moisture sensitive but it can be stored in anhydrous ethereal solvents under argon for at least 24 h without appreciable decomposition. Fig. 1. The C8K network from two orthogonal perspectives. 1887 1888 D. SAVOIA, C. TROMBINI AND A. UMANI-RONCHI Potassium—graphite may be regarded as the heterogeneous polymeric analogue of the radical anion of polynuclear aromatic compounds, and in fact displays a quite similar reactivity, acting principally as a reducing agent through electron transfer processes. Prior to our studies, potassium—graphite found use in a limited number of synthetically useful reactions, for example in the reductions of carbonyl compounds (ref. 3) and transition metal carbonyls (ref. 4). REACTIONS OF POTASSIUM-GRAPHITE (C8K) We found that potassium—graphite can be conveniently employed to reduce a,— unsaturated ketones and carboxylic acids, as well as Schiff's bases, in tetrahydrofuran (THF) to their corresponding saturated compounds (ref. 5) in a kind of heterogeneous Birch reaction (Table 1). The yields are good to excellent, employing an excess of potassium—graphite, and, in the case of ketones, hexamethyldisilazane as cosolvent. Noteworthy, the method offers the advantage of avoiding the troublesome and expensive use of ammonia or amines as well as of poisonous hexamethyiphosphoric triamide (HMPTA) required in the alternative "dissolved metal reduction". Furthermore it allows an easy separation of the organic products from the reaction mixture by filtration. TABLE 1 Substrate Product °C mm Yield (%)

Dimetallation of phenylacetylene. Synthesis of ortho‐substituted derivatives of phenylacetylene, benzo[b]selenophene and benzo[b]tellurophene

Abstract: Phenylacetylene can be dimetallated in two ways. o-K-C6H4-C C - Li is formed by treating phenylacetylene at −70°C with two equivalents of butyllithium and one equivalent of potassium tert-butoxide in a mixture of tetrahydrofuran and hexane. The dimetallation with BuLi-N,N,N′, N′-tetramethylethanediamine (TMEDA) affords a mixture of about 15% (m + p)-Li-C6H4-C C Li and 85% o-Li-C6H4-C C-Li. Ortho-K-C6H4-C C-Li can be transformed into the dilithio or di-Grignard derivatives by addition of anhydrous lithium bromide or magnesium bromide etherate. Reaction of the dilithio derivative with elemental selenium and tellurium, followed by successive addition of tert-butyl alcohol and hexamethylphosphoric triamde (HMPT), gives benzo[b]selenophene and benzo[b]tellurophene in good yields. Regiospecific functionalization of the nucleus via dimetal derivatives succeeds in the case of alkylation, halogenation, sulfenylation and acylation (with dimethylformamide and dimethylacetamide). Trimethylchlorosilane, chloromethyl methyl ether, aldehydes and ketones do not however react regiospecifically.

Rotational freedom of guest molecules in tetrahydrofuran clathrate hydrate as determined by heat capacity measurements

Abstract: Rotation libre au-dessus de 120 K, et augmentation progressive de la rotation genee aux temperatures inferieures

Diastereoselective reduction of chiral α-ketoamides derived from (S)-proline esters with sodium borohydride. Preparation of optically active α-hydroxy acids

Abstract: Diastereoselective reductions of chiral α-ketoamides (3) derived from (S)-proline esters (2) with sodium borohydride were examined. Hydrolysis of the reduction products afforded optically active α-hydroxy acids (5) in good enantiomeric excesses (e.e.). The most influential factor of the asymmetric induction was the effect of using a mixed hydroxylic and non-hydroxylic solvent. The degree of asymmetric induction varied considerably with the ratio of alcohol and tetrahydrofuran (THF) in the mixed solvent. With aromatic ketoamides (3), higher asymmetric induction occurred in a mixed alcohol–THF solvent than in the corresponding individual solvents.

Bimetallic halides. Crystal structure of and ethylene polymerization by vanadium(II) chloride-zinc chloride-tetrahydrofuran (VCl2.ZnCl2.4THF)

Abstract: Activite catalytique elevee pour la polymerisation de C 2 H 4 et encore fortement augmentee par addition d'hydrocarbures halogenes

Organolanthanoids .VIII. Some Ligand-Exchange Reactions of Pentafluorophenyllanthanoids and Bis(Phenylethynyl)Ytterbium(II)

Abstract: The cyclopentadienyl - and indenyl-lanthanoids, (C5H5)2Yb( dme ) ( dme = 1,2- dimethoxyethane ), (C9H7)2Yb( thf )2 ( thf = tetrahydrofuran ), (C5H5)2Eu( thf )n (n = 0.5 or 1), (C9H7)2Eu( thf ), (C5H5)3Sm, (MeC5H4)3Sm, and (C9H7)3Sm( thf ) have been prepared by ligand exchange reactions of (C6F5)2Yb, (C6F5)2Eu, and a pentafluorophenylsamarium species with cyclopentadiene , methylcyclopentadiene , or indene. This synthetic method has particular significance for the indenyllanthanoids . An explosive product was obtained from (C6F5)2Yb and methylcyclopentadiene. Reactions of ( PhCC )2Yb with cyclopentadienes and indene have yielded (C5H5)2Yb( dme ), (MeC5H4)2Yb( dme ), and (C9H7)2Yb( thf )2, but (C5H5)2Yb did not undergo ligand exchange with phenylacetylene.

Purification of solvents for electroanalysis: tetrahydrofuran and dioxane

Abstract: Chairman: J. Jordan (USA); Secretary: K. Izutsu (Japan); Titular Members: A. K. Covington (UK); J. Juillard (France); R. C. Kapoor (India); E. Pungor (Hungary); Associate Members: J. F. Coetzee (USA); W. Davison (UK); R. A. Durst (USA); M. Gross (France); H. Kao (China); K. M. Kadish (USA); R. Kalvoda (Czechoslovakia); Y. Marcus (Israel); T. Mussini (Italy); H. W. NUrnberg (FRG); M. Senda (Japan); D. E. Smith (USA); N. Tanaka (Japan); National Representatives: D. D. Perrin (Australia); B. Gilbert (Belgium); W. C. Purdy (Canada); R. Neeb (FRG); K. Tóth (Hungary); S. K. Rangarajan (India); W. F. Smyth (Ireland); E. Grushka (Israel); Z. Galus (Poland); G. Johansson (Sweden); J. Buffle (Switzerland); B. Birch (UK); J. Osteryoung (USA); M. Branica (Yugoslavia).

Palladium-catalysed conversion of alkenols into five- and six-membered ring lactones at room temperature and atmospheric pressure

Abstract: Unsaturated alcohols react with carbon monoxide, oxygen, palladium chloride, copper(II) chloride, and hydrochloric acid in tetrahydrofuran to give lactones in 42–80% yield.

Pd/Re hydrogenation catalyst for making tetrahydrofuran and 1,4-butanediol

Abstract: Palladium/rhenium-on-carbon catalyst; a method employing said catalyst to produce tetrahydrofuran, 1,4-butanediol or mixtures thereof in selectable ratios from a number of starting reactants; and a method for making the Pd/Re/C catalyst.

Semiconductor photocatalysis. Part 4. Hydrogen evolution and photoredox reactions of cyclic ethers catalysed by zinc sulphide

Abstract: ZnS-catalysed photoredox reactions of aqueous solutions of cyclic ethers, i.e. tetrahydrofuran, dihydrofurans, 2,5-dimethyltetrahydrofuran, 3-methyloxetane, 1,4-dioxane, and tetrahydropyran are described. A freshly prepared ZnS suspension displays efficient and selective photocatalysis especially for furan derivatives under band-gap irradiation (> 290 nm); reduction of water by the conduction band electrons generates H2 and one-hole oxidation of the substrates leads to carbon–carbon bond formation through coupling of intermediary radicals. In the photolysis of tetrahydrofuran, oligomerization from the dimeric product (1) to octamer was observed with efficient H2 evolution (φ½H2= 0.13–0.62). Further oxidation of intermediary radicals and photoreduction of the resulting oxidation products were also confirmed; e.g. photolysis of 2,5-dimethyltetrahydrofuran gave exclusively the ring-opened product (9) with its photoreduced product, hexane-2,5-diol (10).