Tetrahydrofuran toluene solvent systems

Thus, an opposite sense of asymmetric induction was found in the solvent system toluene/HM-PA compared to toluene/ tetrahydrofuran, dioxolane or trimethylamine. Optimized conditions for each electrophile are tetrahydrofuran for iodomethane, dioxolane for allyl and benzyl bromide, and trimethylamine for methyl bromoacetatel8. Starting from a-substituted fl-oxo esters, quaternary asymmetric centers arc generated (see Table 6). 

Several studies have appeared (12,13,14) in which the propagation reactions involving styryllithium were examined in mixed solvent systems comprising benzene or toluene and ethers. The kinetics were examined under conditions where the ether concentration was held constant and the active center concentration varied. In most cases, the kinetic orders of the reactions were identical to those observed in the absence of the ether. Thus, in part, the conclusion was reached (13,14) that the ethers did not alter the dimeric association state of polystyryllithium. The ethers used were tetrahydrofuran, diphenyl ether, anisole, and the ortho and para isomers of ethylanisole. 

One of the major uses of activated carbon is in the recovery of solvents from industrial process effluents. Dry cleaning, paints, adhesives, polymer manufacturing, and printing are some examples. Since, as a result of the highly volatile character of many solvents, they cannot be emitted directly into the atmosphere. Typical solvents recovered by active carbon are acetone, benzene, ethanol, ethyl ether, pentane, methylene chloride, tetrahydrofuran, toluene, xylene, chlorinated hydrocarbons, and other aromatic compounds [78], Besides, automotive emissions make a large contribution to urban and global air pollution. Some VOCs and other air contaminants are emitted by automobiles through the exhaust system and also by the fuel system, and activated carbons are used to control these emissions [77,78],... 

Table 3 gives the third-order nonlinear optical properties of bioengineered polymers prepared by enzyme-catalyzed polymerization using horseradish peroxidase in biphasic solvent systems. Water-immiscible solvents used for the biphasic media are benzene, chloroform, toluene, tetrahydrofuran, and isooctane. Third-order nonlinear optical properties of homopolymers and copolymers prepared in biphasic solvent systems are similar to those of polymers prepared in monophasic systems. The values of polyaromatic amines solutions measured at 532 nm are one to two orders higher than the x values observed with polyphenolic compounds. Third-order nonlinear optical properties of copolymers of aromatic amines with... 

Toluene is a useful co-solvent in metal-ammonia reductions as first reported by Chapman and his colleagues. The author has found that a toluene-tetrahydrofuran-ammonia mixture (1 1 2) is a particularly useful medium for various metal-ammonia reductions. Procedure 8a (section V) describes the reduction of 17-ethyl-19-nortestosterone in such a system. Ethylene dibromide is used to quench excess lithium. Trituration of the total crude reduction product with methanol affords an 85% yield of 4,5a-dihydro-17-ethyl-19-nortestosterone, mp 207-213° (after sintering at 198°), reported mp 212-213°. For the same reduction using Procedure 5 (section V), Bowers et al obtained a 60% yield of crude product, mp, 196-199°, after column chromatography of the total reduction product. A similar reduction of 17-ethynyl-19-nortestosterone is described in Procedure 8b (section V). The steroid concentration in the toluene-tetrahydrofuran-ammonia system is 0.05 M whereas in the ether-dioxane-ammonia system it is 0.029 M. 

General Considerations. The following chemicals were commercially available and used as received 3,3,3-Triphenylpropionic acid (Acros), 1.0 M LiAlH4 in tetrahydrofuran (THF) (Aldrich), pyridinium dichromate (Acros), 2,6 di-tert-butylpyridine (Acros), dichlorodimethylsilane (Acros), tetraethyl orthosilicate (Aldrich), 3-aminopropyltrimethoxy silane (Aldrich), hexamethyldisilazane (Aldrich), tetrakis (diethylamino) titanium (Aldrich), trimethyl silyl chloride (Aldrich), terephthaloyl chloride (Acros), anhydrous toluene (Acros), and n-butyllithium in hexanes (Aldrich). Anhydrous ether, anhydrous THF, anhydrous dichloromethane, and anhydrous hexanes were obtained from a packed bed solvent purification system utilizing columns of copper oxide catalyst and alumina (ether, hexanes) or dual alumina columns (tetrahydrofuran, dichloromethane) (9). Tetramethylcyclopentadiene (Aldrich) was distilled over sodium metal prior to use. p-Aminophenyltrimethoxysilane (Gelest) was purified by recrystallization from methanol. Anhydrous methanol (Acros) was... 

Miscibility is an important consideration when selecting solvents for use in biphasic systems. Table 4.4 shows the miscibility of three ionic liquids with water and some organic solvents. [bmim][PFe] was found to be miscible with organic solvents whose dielectric constant is higher than 7, but was not soluble in less polar solvents or in water. Basic [bmim][AlCl4] was found to react with protic solvents, and the acidic form also reacted with acetone, tetrahydrofuran and toluene. 

The high-pressure phase behavior of polymer-solvent-supercritical carbon dioxide systems was investigated experimentally The polymers used were poly(methyl methacrylate), polystyrene, polybutadiene, and poly(vinyl ethyl ether) at concentrations ranging from 5 to 10% in mixtures with toluene or tetrahydrofuran. The experiments were conducted for temperatures from 25 to 70°C and pressures up to 2200 psi in a high-pressure cell (Kiamos and Donohue, 1994). 

A new system for grafting copolymerization was described by Kojima and collaborators (126), in 1971, involving tri-n-butyl borane and water, at 37° C, for 2 hrs, in a taper joint glass tube. This system was inefficient when organic solvents like cyclohexanone, n-hexane, tetrahydrofurane, and toluene were used instead of water. 

That the reductive cleavage is compatible with the presence of 0-acyl groups raises the question of whether the regioselectivity may be changed back to that of LiptSk-Ntoisi. Indeed, when the solvent is changed from tetrahydrofuran to toluene and the reduction system to MejNBHj-AlClj, a free 6-OH and O-benzyl at C-6 is produced (Scheme 9) [27]. 

Further difficulties arise in explaining the solvent dependence in opening the rings using the MejNBHj-AiClj system. The expected stronger solvation of AICI3 in tetra-hydrofuran, versus toluene or dichloromethane, would indicate preferential electrophilic attack at 0-6 in tetrahydrofuran, and the production of the 4-benzyl ether, contrary to what is observed. 

Various organic solvents were tested for the PLE-catalyzed asymmetric hydrolysis of diester (12) in a biphasic system. The results (Table 5) indicate that the reaction yields and e.e. of monoester (13) were dependent on the solvent used in the asymmetric hydrolysis. Tetrahydrofuran (THF), methyl isobutyl ketone (MIBK), hexane, and dichloromethane inhibited PLE. Lower reaction yields (28-56 M%) and lower e.e. (59-72%) were obtained using f-butyl methyl ether, dimethylformamide (DMF), and dimethylsulfoxide (DMSO) as cosolvent. Higher e.e. (>91%) was obtained using methanol, ethanol, and toluene as cosolvent. Ethanol gave highest reaction yield (96.7%) and e.e. (96%) for monoester (13). 

This can be exploited for the extractive separation of fluorous-tagged compounds from other substances. The partition coefficient depends on the size of the fluorous tag and on the organic solvent. The preference for the fluorous phase increases with increasing fluorine content and polarity of the organic phase. As the fluorous solvent, FC-72 (a mixture of CeFu isomers) is often used. At room temperature, it forms biphasic systems with solvents such as toluene, dichloromethane or acetonitrile and with aqueous media. Somewhat surprisingly, diethyl ether and tetrahydrofuran are good solvents for fluorous molecules and are miscible with FC-72 at... 

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