Tetrahydrofuran alkane

Alkane/alcohols Alkane / tetrahydrofuran Alkane/dioxan Chlorinated solvents... 

The a-lithiated sulfides 33 are another class of chiral organometallic reagent, readily available by deprotonation of the parent l-(phcnylthio)alkanes 32 with butyllithium in tetrahydrofuran at - 78 °C. 

Aqueous solutions are not suitable solvents for esterifications and transesterifications, and these reactions are carried out in organic solvents of low polarity [9-12]. However, enzymes are surrounded by a hydration shell or bound water that is required for the retention of structure and catalytic activity [13]. Polar hydrophilic solvents such as DMF, DMSO, acetone, and alcohols (log P<0, where P is the partition coefficient between octanol and water) are incompatible and lead to rapid denaturation. Common solvents for esterifications and transesterifications include alkanes (hexane/log P=3.5), aromatics (toluene/2.5, benzene/2), haloalkanes (CHCI3/2, CH2CI2/I.4), and ethers (diisopropyl ether/1.9, terf-butylmethyl ether/ 0.94, diethyl ether/0.85). Exceptionally stable enzymes such as Candida antarctica lipase B (CAL-B) have been used in more polar solvents (tetrahydrofuran/0.49, acetonitrile/—0.33). Room-temperature ionic liquids [14—17] and supercritical fluids [18] are also good media for a wide range of biotransformations. 

Although the unsaturated nitrile oxides 124 can be prepared via the aldoxime route (see Scheme 8), the older procedure suffers from the disadvantage that a tenfold excess of allyl alcohol and two additional steps are required when compared to Scheme 15. Therefore, unsaturated nitro ether 123 that can be prepared by condensation of an aldehyde 120 and a nitro alkane followed by Michael addition of alcohol 122, was a useful precursor to nitrile oxide 124 [381. The nitrile oxide 124 spontaneously cyclized to ether 125. This procedure is particularly suitable for the synthesis of tetrahydrofurans (125a-h) and tetrahydropyrans (125i-k) possessing Ar substituents in 72-95% yield (Table 12). The seven-membered ether 1251 was obtained only in 30% yield on high dilution. The acetylenic nitro ether 126 underwent INOC reaction to provide the isoxazole 127. 

Fig. 3. Linear alkane product distribution as obtained in methanol, heptane, and tetrahydrofuran at 300°C with an initial CO/H2 = 1/1 pressure of 100 bar. (Reproducibility of kt/k2 figures not better than 1.)...

Alkyl alkanoates are reduced only at very negative potentials so that preparative scale experiments at mercury or lead cathodes are not successful. Phenyl alkanoates afford 30-36% yields of the alkan-l-ol under acid conditions [148]. Preparative scale reduction of methyl alkanoates is best achieved at a magnesium cathode in tetrahydrofuran containing tm-butanol as proton donor. The reaction is carried out in an undivided cell with a sacrificial magnesium anode and affords the alkan-l-ol in good yields [151]. In the absence of a proton donor and in the presence of chlorotrimethylsilane, acyloin derivatives 30 arc formed in a process related to the acyloin condensation of esters using sodium in xylene [152], Radical-anions formed initially can be trapped by intramolecular addition to an alkene function in substrates such as 31 to give aiicyclic products [151]. 

In polar and H-bonding solvents such as acetone, tetrahydrofuran or methanol CgQ is essentially insoluble. It is sparingly soluble in alkanes, with the solubility increasing with the number of atoms. In aromatic solvents and in carbon disulfide, in general appreciable solubilities are observed. A significant increase of the solubility takes place on going from benzenes to naphthalenes. Although there are trends for the solution behavior of Cjq, there is no direct dependence of the solubility on a certain solvent parameter like the index of refraction n. When the solubility is... 

Die Uberfiihrung von Alkenen in vie.-Diamino-alkane gelingt in mittleren Ausbeuten in einer Eintopfreaktion durch Umsetzung des Alkens mit 0,5 mol-Aquivalenten Bis-[ben-zonitrilj-palladium-dichlorid in Tetrahydrofuran bei 0°, Zugabe eines Uberschusses von sekundarem Amin und Oxidation des so gebildeten Aminoalkyl-palladium-Komplexes... 

Saturated alkane-1,2-carboxylic acids and alkane-1,3-carboxylic acids give, in general, three types of products bis(trifluoromethyl)alkancs, cyclic a,a,a, a -tetrafluoro ethers and linear bis(pentafluoroalkyl) ethers. The 1,2-dicarboxylic acids, succinic and halosuccinic acids, give as the main products the cyclic ethers 6, derivatives of tetrahydrofuran, in ca. 30-50% yield, but from 1,3-dicarboxylic acids the yields of the corresponding six-membered ethers 9 are 16%.118... 

A class of compounds of the general formula (XIV) can be prepared by two types of reaction the action of the polymethylenedimagnesium dibromide on 1,2-dichlorotetramethyldisilane in tetrahydrofuran, and sodium-potassium condensation of a,a>-bis (chlorodimethylsilyl)alkanes in benzene- -heptane solution (124). 

The data indicate that as the reduced density of a fluid is increased the cybotatic region becomes more polar/polarizable, with an especially large effect for supercritical NH3. The low it values for Freon-13 at these densities are similar to those of the perfluoro-alkanes ( 5). The values for supercritical C02 and N20 range between those of the perfluoro-alkanes to that of the n-alkanes (n-heptane, etc.) 5). Ammonia gives it values which range from approximately that of n-heptane to that of ethyl acetate or tetrahydrofuran ( 5) over the density range studied. 

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