Tetrahydrofurans, from hydrocarbon

Palladium acetate on silica remains in a dissolved state in the ionic liquid in the pores of silica when it is prepared by evaporation of tetrahydrofuran from a Pd(0Ac)2/Si02/[BMIm]PF6 mixture [44]. Atomic force microscopy revealed a smooth surface of the silica. Mizoroki-Heck reactions of iodo- and bromobenzene carried out with various acrylates in hydrocarbon solvents resulted in an easy separation of catalyst and product. Leaching of the catalyst into the hydrocarbon solvent occurred to less than 0.24%. The catalyst was successfully recycled and reused six times with conserved activity. 

A variant of the Wurtz reaction is the preparation of tetrabutyltin from activated magnesium chips, butyl chloride, and stannic chloride in a hydrocarbon mixture. Only a small amount of tetrahydrofuran is required for the reaction to proceed in high yield (86). 

This complex should be used when the organolithium is in solution in a hydrocarbon solvent. For organolithium reagents prepared in ether (see Note 4), the same complex may be used or, more conveniently, copper iodide (Cull can be used. The Cul purchased from Prolabo or Merck 4 Company, Inc. may be used directly. Other commercial sources of Cul (Fluka, Aldrich Chemical Company, Inc., Alfa Products, Morton/Thiokol, Inc.) furnish a salt which affords better results when purified. 1 mol of Cul is stirred for 12 hr with 500 ml of anhydrous tetrahydrofuran, then filtered on a sintered glass funnel ( 3), washed twice with 50 ml of anhydrous tetrahydrofuran, once with 50 ml of anhydrous ether and finally dried under reduced pressure (0.1 imO for 4 hr. 

Reductive removal of fluorme from alk I fluorides requires a potent reducing agent and so is not noimally encountered However, hydrogenolysis of an unacuvated carbon-fluorine bond in, for example, 3 (3-fluorocholestane has been efficiently accomplished in 88% yield with a solution of potassium and dicyclohexyl 18 crown-6 in toluene at 25 C [/] Similarly, sodium naphthaiene in tetrahydrofuran converts 6 tluorohexene-1 and 1-fluorohexane to hydrocarbons in 50% yield at 25 C over a 7-h penod [2]... 

Polymerization of triphenylmethyl methacrylate in the presence of a chiral anion catalyst results in a polymer with a helical structure that can be coated onto macroporous silica [742,804). Enantioselectivity in this case results from insertion and fitting of the analyte into the helical cavity. Aromatic compounds and molecules with a rigid nonplanar structure are often well resolved on this phase. The triphenylmethyl methacrylate polymers are normally used with eluents containing methanol or mixtures of hexane and 2-propanol. The polymers are soluble in aromatic hydrocarbons, chlorinated hydrocarbons and tetrahydrofuran which, therefore, are not suitable eluents. 

The initiation reaction in the polymerization of vinyl ethers by BF3R20 (R20 = various dialkyl ethers and tetrahydrofuran) was shown by Eley to involve an alkyl ion from the dialkyl ether, which therefore acts as a (necessary) co-catalyst [35, 67]. This initiation by an alkyl ion from a BF3-ether complex means that the alkyl vinyl ethers are so much more basic than the mono-olefins, that they can abstract alkylium ions from the boron fluoride etherate. This difference in basicity is also illustrated by the observations that triethoxonium fluoroborate, Et30+BF4", will not polymerise isobutene [68] but polymerises w-butyl vinyl ether instantaneously [69]. It was also shown [67] that in an extremely dry system boron fluoride will not catalyse the polymerization of alkyl vinyl ethers in hydrocarbons thus, an earlier suggestion that an alkyl vinyl ether might act as its own co-catalyst [30] was shown to be invalid, at least under these conditions. 

Apart from the conversion of peroxides to useful products, it is sometimes necessary to reduce peroxides, and especially hydroperoxides formed by auto-oxidation. Such compounds are formed especially in hydrocarbons containing branched chains, double bonds or aromatic rings, and in ethers such as diethyl ether, diisopropyl ether, tetrahydrofuran, dioxane, etc. Since most peroxidic compounds decompose violently at higher temperatures and could cause explosion and fire it is necessary to remove them from liquids they contaminate. Water-immiscible liquids can be stripped of peroxides by shaking with an aqueous solution of sodium sulfite or ferrous sulfate. A simple and efficient way of removing peroxides is treatment of the contaminated compounds with 0.4 nm molecular sieves [669]. 

Reduction of esters by trichlorosilane in tetrahydrofuran in the presence of tert-butyl peroxide and under ultraviolet irradiation gave predominantly ethers from esters of primary alcohols, while esters of tertiary alcohols were cleaved to acids and hydrocarbons. Esters of secondary alcohols gave mixtures of ethers and acids/hydrocarbons in varying ratios. 1-Adamantyl trimethylacetate, for example, afforded 50-100% yields of mixtures containing 2-42% of 1-adamantyl neopentyl ether and 58-98% of adamantane and trimethylacetic acid [1033]. 

Among simple hydrocarbon ions, the distonic trhnethylene radical cation. CH2CH2CH2+ (7 +) is accessible upon internal excitation of the cyclopropane molecular ion or by loss of formaldehyde from the tetrahydrofuran... 

Heats of adsorption measurements do not lead to very specific interpretation since the isosteric heat of adsorption (AH) arises from both nonspecific interactions, which occur in all cases of adsorption, and from specific interactions with the hydroxy groups nevertheless, valuable conclusions about the binding forces can be deduced. Saturated hydrocarbons, e.g., n-pentane, have a value of — AH of 8.0 kcal/mole, while saturated ethers have values of around 16 kcal/mole.14 Probably dispersion forces only are involved in the former case and additional specific interaction with the silanol-OH occurs in the second case. On graphite, where there is no specific interaction, the heats of adsorption of hydrocarbons and ethers are very similar.17 The heat of adsorption of furan (11 kcal/mole) is 5 kcal/mole less than that of tetrahydrofuran this again indicates the effect that delocalization of electrons by the double bonds has on the binding forces.14... 

The ions (w) resulting from loss of cyclopropane from the molecular ions were only observed for the sulfur, selenium and tellurium analogues. The alternative mode of fragmentation in which the hydrocarbon fragment (y) carries the charge provides the base peak for the tetrahydrofuran spectrum, but is only a minor feature of the spectra of the selenium and tellurium analogues. The hydrocarbon ion C4H/ (z) is a minor feature of the tetrahydrothiophene spectrum but provides the base peak of the spectra of the selenium and tellurium analogues. 

Copolymerizations initiated by lithium metal should give the same product as produced from lithium alkyls. Usually the radical ends produced by electron transfer initiation have so short a lifetime they can have no influence on the copolymerization. This is true for instance in the copolymerization of isoprene and styrene (50). The product is identical if initiated by lithium metal or by butyllithium. With the styrene-methylmethacrylate system, however, differences are observed (79,80,82). Whereas the butyllithium initiated copolymer contains no styrene at low conversions, the one initiated by lithium metal has a high styrene content if the reaction is carried out in bulk and a moderate one even in tetrahydrofuran. These facts led O Driscoll and Tobolsky (80) to suggest that initiation with lithium occurs by electron exchange and that in this case the radical ends are sufficiently long-lived to produce simultaneous radical and anionic reactions at opposite ends of the chain. Only in certain rather exceptional circumstances would the free radical reaction be of importance. Some of the conditions required have been discussed by Tobolsky and Hartley (111). The anionic reaction should be slow. This is normally true for lithium based catalysts in hydrocarbon solvents. No evidence of appreciable radical participation is observed for initiation by sodium and potassium. The monomers should show a fast radical reaction. If styrene is replaced by isoprene, no isoprene is found in the copolymer for isoprene polymerizes slowly by free radical initiation. Most important of all, initiation should be slow to produce a low steady concentration of radical-anions. An initiator which produces an almost instantaneous and complete electron transfer to monomer produces a high radical concentration which will ensure their rapid mutual termination. 

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