Furan, tetrahydro-, compound with

The HDO and isomerization reactions were previously described as bimolecular nucleophilic substitutions with allylic migrations-the so-called SN2 mechanism (7). The first common step is the fixation of the hydride on the carbon sp of the substrate. The loss of the hydroxyl group of the alcohols could not be a simple dehydration -a preliminar elimination reaction- as the 3-butene-l-ol leads to neither isomerization nor hydrodehydroxyl at ion (6). The results observed with vinylic ethers confirm that only allylic oxygenated compounds are able to undergo easily isomerization and HDO reactions. Moreover, we can note that furan tetrahydro and furan do not react at all even at high temperature (200 C). 

According to Freifelder, in most instances ruthenium catalyst is superior to nickel catalyst for the hydrogenation of furans to tetrahydrofurans the hydrogenation can be carried out at 70-100°C and 7 MPa H2.185 He refers to an example in which 2-furfu-rylamine was hydrogenated without solvent over ruthenium dioxide at 100°C and 8 MPa H2 in 10 min, compared to the temperatures of < 150°C and a reaction time of 30 h at 7 MPa H2 that were required for hydrogenation with Raney Ni. Hydrogenation of P-(2-furyl)alkylamines and an A-ethyl-2-furylalkylamine to the corresponding tetrahydro compounds was performed satisfactorily over palladium catalyst in ethanol in the presence of hydrochloric acid at room temperature and 0.62 MPa H2 (eq. 12.102)197 and over 5% Rh-C in neutral solvent at room temperature and 0.15 MPa... 

Cahiez, Knochel, and co-workers have developed a mixed catalytic system consisting of MnBr2/GuGl and diethyl-zinc in iV,A -dimethylpropyleneurea (DMPU), which can be used for the stereocontrolled formation of tetrahydro-furan organozinc compounds from readily available unsaturated bromoacetals. The organozinc compounds are readily transmetalated with GuGN-2LiGl, and upon treatment with ethyl (o -bromomethyl)acrylate or ethyl propiolate homoallyl- and allyl-substituted bicyclic tetrahydrofurans are obtained in 71% and 63% yield (Scheme 70). 

The diacetylene 15 readily underwent Diels-Alder cycloaddition with furan to furnish the endoxide 16, which was hydrogenated catalytically to the tetrahydro compound 17. Dehydration of 77 with polyphosphoric acid gave 1 in 16% yield (Eq. 7) Alternatively, deoxy nation of 16 with low valent titanium generated by reducing titanium tetrachloride with lithium aluminium hydride also afforded 7 in 50% yield... 

Furans are volatile, fairly stable compounds with pleasant odours. Furan itself is slightly soluble in water. It is readily available, and its commercial importance is mainly due to its role as the precursor of the very widely used solvent tetrahydro-furan (THF). Furan is produced by the gas-phase decarbonylation of furfural (2-formylfuran, furan-2-carboxaldehyde), which in turn is prepared in very large quantities by the action of acids on vegetable residues, mainly from the manufacture of porridge oats and cornflakes. Furfural was first prepared in this way as far back as 1831 and its name is derived from furfiir, which is the latin word for bran in due course, in 1870, the word furan was coined from the same root. 

PTM radical forms beautiful crystalline inclusion compounds with benzene, fluorobenzene, chlorobenzene, toluene, 1,4-dioxane, tetrahydro-furane, cyclohexane and cyclohexene the host guest ratio being 1 1 for roost of them. Those compounds are stable towards vaccurom drying at room temperature but on heating a release of the guest molecules takes place at different temperatures. 

Na-naphthalene complex in tetrahydrofuran is acetylene derivatives and certain compounds with A rapid stream of cooled acetylene passed into ice-salt cooled tetrahydrofuran at —15° with simultaneous addition of small portions of a soln. of Na in naphthalene-tetrahydrofuran so that decoloration takes place after each addition, then a soln. of cyclohexanone-tetrahydro-furan (1 1) added dropwise at —15° with vigorous stirring, which is continued overnight 1-ethynylcyclohexanol. Y 90%. 

In recent years, a great diversity of structurally well-defined functionalized fullerenes has been designed and synthesized for that purpose. Some of them exhibit pronounced solubility in water (vide infra). But even for compounds being virtually insoluble in water, stable aqueous phases can be obtained in plenty of cases by diluting stock solutions of the compounds in polar organic solvents with various amounts of water. Notably, dimethyl sulfoxide (DMSO) and tetrahydro-furan (THF) have turned out to be excellent surfactants for preparing stable aqueous fullerene solutions (Angelini et al., 2005 Cassell et al., 1999 Da Ros et al., 1996 Gun kin et al., 2006 Illescas et al., 2003). Also cosolvents such as dimethylforma-mide (DMF) and methanol can be used to promote water solubility. After subsequent dilution of a saturated solution of C60 in benzene with THF, acetone and finally water, actually stable aqueous suspensions of pristine fullerene can be obtained (Scrivens et al., 1994). 

Less polar organic compounds such as acetonitrile and tetrahydro-furan have also been used as modulators with nonpolar aMphatic hydrocarbons as eluent. With decreasing polarity of the additive the concentration of modulator in the nonpolar eluent has to be inci ased in order to obtain similar retention values. Approximately the same k values for diphenoxybenzene are achieved with either 0.0S%(v/v)of acetonitrile or 10% (v/v) of dichloromethane in n-hexane 47). As discussed above, the latter case corresponds to an eluent mixture rather than a modulated system. 

Waack and Doran [26] reported on the relative reactivities of 13 structurally different organolithium compounds in polymerization with styrene in tetrahydro-furan at 20°C. The reactivities were determined by the molecular weights of the formed polystyrene. The molecular weights are inversely related to the activity of the respective organolithium polymerization initiators. Reactivities decreased in the order alkyl > benzyl > allyl > phenyl > vinyl > triphenylmethyl as shown in Table 3.1. 

FigurB 25-26 Application of the method development triangle to the separation of seven aromatic compounds by HPLC. Column 0.46 x 25 cm Hypersil ODS (C)e on 5-(j.m silica) at ambient temperature ( 22°C). Elution rate was 1.0 mL/min with the following solvents (A) 30 vol% acetonitrile/70 vol% buffer (B) 40% methanol/60% buffer (C) 32% tetrahydrofuran/68% buffer. The aqueous buffer contained 25 mM KH2P04 plus 0.1 g/L NaN3 adjusted to pH 3.5 with HCI. Points D, E, and F are midway between the vertices (D) 15% acetonitrile/20% methanol/65% buffer (E) 15% acetonitrile/16% tetrahydrofuran/69% buffer (F) 20% methanol/16% tetrahydrofuran/64% buffer. Point G at the center of the triangle is an equal blend of A, B, and C with the composition 10% acetonitrile/13% methanol/11% tetrahydro-furan/66% buffer. The negative dip in C between peaks 3 and 1 is associated with the solvent front. Peak identities were tracked with a photodiode array ultraviolet spectrophotometer (1) benzyl alcohol (2) phenol (3) 3, 4 -dimethoxyacetophenone (4) m-dinitrobenzene (5) p-dinitrobenzene ...

The most import uni cyclic ethers arc (he furan compounds Furfural is manufactured by treating pentosan with sulfuric acid and steam stripping mil the furfural a n is formed The sources of pentosan arc such agricultural products uv comet tbs. oat hulls, and hagavtc Furfural is used to produce furan and tetrahydro furan fTHF) These products are used as organic intermediates, extraction solvent, polymer solvents, and in polyurethane applications... 

Other attempts to avoid the experimental difficulties of measuring the thermal properties of gas hydrates have been to choose the easier route of thermal property measurements of cyclic ethers-ethylene oxide (EO) for structure I, or tetrahydro-furan (THF) for structure II. Since both compounds are totally miscible with water, liquid solutions can be made at the theoretical hydrate compositions (EO 7.67H20 or THF 17H20). 

Milled rigid sheets of poly (vinyl chloride) on heating at 185°C. lose weight at a rate which increases with time. By polymer fractionation procedures, it was shown the rate of hydrogen chloride loss increases as the content of tetrahydro-furan-insoluble resin increases. The insoluble resin content accumulates at a rate which depends, in part, on the additive present. This insolubilization reaction is catalyzed by cadmium compounds. The increased dehydrochlorination rate of the insoluble crosslinked resins may result from the susceptibility of the crosslinked structures to oxidation and from the subsequent thermal degradation of the oxidation products. The effects of various common additives on the rates of insolubilization and weight loss are described. 

Oxocyclopentyl and 3-oxocyclohexyl phenyl tellurium compounds reacted in tetrahydro-furan with butyraldehyde and benzaldehyde. The products of these aldol reactions were not isolated, but oxidized to the telluroxides that, in turn, were converted to enones by telluroxide elimination4. 

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