And ether solvents

The group 4B metallocene dicarbonyls exhibit excellent solubility in aromatic and ethereal solvents and very good solubility in aliphatic solvents. In most cases the dicarbonyls can be purified by recrystallization from aliphatic solvents at about -20°C (58,59) and/or by sublimation at 70-80°C and 10 1 2-10 3 mm Hg (6-8,24). 

Scheme 2. Reaction between LiAsFe and Ether Solvents...

A -sulfinylacetamide 297 in greater than 90% yield when a catalytic amount of methyltrioxorhenium is employed. Futhermore, the hetero-Diels-Alder adduct is highly soluble in both chlorinated and ethereal solvents. A detailed investigation of the retro-Diels-Alder reaction of 298 by thermogravimetric analysis revealed an onset temperature of 120 °C and complete conversion of bicycle 298 to pentacene 296 at 160 °C, which are temperatures compatible with the polymer supports typically used in electronics applications. The electronic properties of these newly prepared OTFTs are similar to those prepared by traditional methods. Later improvements to this chemistry included the use of A -sulfinyl-/< r/-butylcarbamate 299 as the dienophile <2004JA12740>. The retro-Diels-Alder reaction of substrate 300 proceeds at much lower temperatures (130 °C, 5 min with FlTcatalyst 150 °C, Ih with no catalyst). 

Bi N(SiMe3)2 36 is an extremely air-sensitive, pale yellow microcrystalline compound that is very soluble in hydrocarbon and ether solvents. It is much less photosensitive than Bi(NMe2)3. H and 13C H NMR spectra at room temperature in d8-toluene show signals at 8 0.55 and 7.51 respectively. 

Bis(TADB)iron(II) is soluble in aromatic and etheric solvents and in CHCI3. It is unsublimable, does not react with cyclopentadiene at 150°, and while it is relatively stable against bases, amines and alcohols, it is readily decomposed by acids. 

Transfers of hydride from boron or lithium to carbon usually occur in the context of addition of the complete M—H moiety to polar or non-polar unsaturation. Additions of boranes to alkenes have been extensively reviewed (Brown et al., 1983a), but the experimental characterization of the hydroboration transition state remains problematic. Dialkylboranes, including 9-borabicyclo[3.3.1]nonane (Wang and Brown, 1980), borinane (Brown et al., 1984), and disiamylborane (Chandrasekharan and Brown, 1985) have now been shown to be dimeric in hydrocarbon and ethereal solvents. With unreactive alkenes, their additions are first order in alkene and half order in the dimer. With reactive terminal alkenes, the reactions are first order only in dimer, with intermediate behaviour between these extremes. A reaction scheme (10) involving reaction of monomeric borane with the alkene satisfies the data, with the observed order depending on the ratio k i/k2. 

Donor numbers of various solvents are listed in Table 3. The values range between 0 and about 60 kcal/mole. Polar solvents such as nitromethane are very weak donors. Solvents such as acetonitrile and propylenecarbonate are moderately strong donors. Ketone, ester, and ether solvents show medium donor properties. Amides and sulfones are strongly basic solvents with donor numbers 25 to 30, and aliphatic amines are very strong donors. 

The yellow crystalline material is very air sensitive. When stored for long periods of time, it should be kept cold, or it will darken and become tacky. The compound is very soluble in hydrocarbon and ether solvents and is slightly proton-ated by alcohols. It decomposes when exposed to halocarbon solvents. 

Pfizer have developed a solvent selection tool, which has been used to educate researchers about solvent replacement and has resulted in reduced amounts of chlorinated and ethereal solvents being used in their research labs. A reduced availability of less desirable solvents also encouraged the uptake of alternatives. For example, hexane was replaced by heptane in stockrooms. The chart shown in Figure 1.5 could be applied to other industries and is easily used in academic research labs. It has been modified to take into account the findings of Fischer and co-workers, and as a result acetonitrile and THF have been transferred from usable to undesirable based on their performance in LCA. 

The reaction is remarkably general for several different aldehydes, as illustrated by the data in Seh. 48 obtained with the triphenylsilyl catalyst derivative. Toluene is the optimum solvent for this reaction—it was found that more polar solvents lead to lower selectivity and ethereal solvents greatly retarded the rate of the reaction. For example, in dichloromethane the asymmetric induction for the reaction of 374 with benzalde-hyde drops from 95 to 82 % ee. 

In order to study the factors determining the regioselectivity of sodium borohydride reduction of a, -unsaturated ketones, reactions with 3-methylcyclohexenone, carvone and cholestenone were carried out in 2-propanol, diglyme, triglyme or pyridine. Mixtures of 1,2- and 1,4-reduction products were obtained in the alcoholic and ether solvents, whereas pure 1,4-reduction was observed in pyridine. Addition of triethylamine to NaBH4 in diglyme led to formation of triethylamine borine, EtsN BHs. Similarly, with pyridine, pyridine borine could be isolated, leading to exclusive 1,4-reductions. 

In the case of isoprene, low molecular weight model compounds (dimer, trimer, etc.) can be prepared in benzene to produce oligomeric analogues of the polyisoprenyllithium active in polymerization [195]. The NMR spectra of such oligomers show that cis and trans forms of the lithium bearing terminal unit occur, and that one predominates at room temperature [195, 196]. It is probably the cis form, although this is difficult to establish without doubt. Except for the one unit chain, the cis—trans ratio varies reversibly with temperature. Transfer to tetrahydro-furan-rich mixtures at low temperatures shows that isomerization occurs when the solution is warmed to —40°C, probably to the trans form. This is the stable form in such solvents at all temperatures. The NMR spectra are basically the same in both hydrocarbon and ether solvents. Only the resonance due to the proton on the y-carbon is shifted upfield in polar... 

Use of nonpolar solvents such as toluene produced higher enantioslectivities than polar solvents such as CH2CI2 and ether solvents, and lowering the temperature gradually increased the optical yield. 

Sodium is commonly used as a drying agent for hydrocarbon and ether solvents. The disposal of excess Na must be carried out with care and usually involves the reaction of Na with propan-2-ol to give H2 and NaOCHMe2. This is a less vigorous, and therefore safer, reaction than that of Na with H2O or a low molecular mass alcohol. An alternative method for disposing of small amounts of Na involves adding H2O to a... 

The compound is soluble without decomposition in hydrocarbon and ether solvents as well as in acetone, benzene, and toluene. It slowly reacts with halocarbon and coordinating solvents. The solid state molecular structure is that of a folded dimer, and it is dimeric also in solution. NMR (CeDi2) 5 1.62 (Cp ), 4.82 (OMe). 

A number of acyclic <7-dialkoxyphosphoranes (18) have been prepared in moderate to high yields by the reaction of bromotriphenylphosphonium bromide (17) with the relevant sodium alkoxide in alcohol and ethereal solvents. The method offers obvious advantages over the peroxide route and in some cases (R=Pr ) higher yields than the Mitsunobu reaction but at the... 

Solubility sol hydrocarbon and ethereal solvents, but should be used at low teir ierature in the latter solvent type half-lives in diethyl ether and THF have been reported reacts violently with H2O and other protic solvents. 

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