Toluene as solvent

Use as Solvent. Toluene is more important as a solvent than either benzene or xylene. Solvent use accounts for ca 14% of the total U.S. toluene demand for chemicals. About two-thirds of the solvent use is in paints and coatings the remainder is in adhesives, inks, pharmaceuticals, and other formulated products utilizing a solvent carrier. Use of toluene as solvent in surface coatings has been declining, primarily because of various environmental and health regulations. It is being replaced by other solvents, such as esters and ketones, and by changing the product formulation to use either fully soHd systems or water-based emulsion systems. 

For the case of MMA polymerization with a source of f-butoxy radicals (DBPOX) as initiator and toluene as solvent, most initiation may be by way of solvent-derived radicals"1"" (Scheme 3.9). Thus, a high proportion of chains (>70% for 10% w/v monomers at 60 °C22) will be initiated by benzyl rather than 1-butoxy radicals. Other entities with abstractable hydrogens may also be incorporated as polymer end groups. The significance of these processes increases with the degree of conversion and with the (solvent or impurity) monomer ratio. 

One of the first published microwave-assisted synthesis of benzothiazoles is the condensation of a dinucleophile such as 2-aminothiophenol, with an ortho-ester (neat) in the presence of KSF clay in a mono-mode microwave reactor operating at 60 W under a nitrogene atmosphere [ 12] (Scheme 12). Traditional heating (oil bath, toluene as solvent and KSF clay) gave the expected products in similar yields compared to the microwave experiments but more than 12 h were required for completion. Solvent-free microwave-assisted syntheses of benzothiazoles was also described by attack of the dinucleophiles cited above on benzaldehydes and benzaldoximines [13] (Scheme 12). This methodology was performed in a dedicated monomode microwave reactor... 

Four mmoles of malononitrile and benzaldehyde were introduced in a batch stirred tank reactor at 323 K with toluene as solvent (30 ml). Then 0.05 g of aluminophosphate oxynitride was added. Samples were analysed by gas chromatography (Intersmat Delsi DI200) using a capillary column (CPSilSCB-25 m). Care was taken to avoid mass or heat transfer limitations. Before the reaction no specific catalyst pretreatment was done. 

Kulin, L.-I., Flodin, P., Ellingsen, T., and Ugelstad, J., Monosized polymer particles in size exclusion chromatography. I. Toluene as solvent, /. Chromatogr., 514, 1, 1990. 

We hoped to define conditions that would allow us to use toluene as solvent for the reaction. The toluene solution of 8 could be taken directly into the dehydrogenation following distillation to remove water and alcohol solvents. The boiling point of toluene was suitable for the thermolysis but silylation in toluene was very slow. 

The aniline was being phosgenated in toluene as solvent, the reaction ran wild and ejected more than 3 tonnes of reactor contents. This is believed to have been due to water contamination, possibly as ice. An initial charge of only part of the phosgene failed to show the exotherm anticipated if water was present, however this may not have been enough, nor was the thermocouple immersed in the solvent. See Diprotium monoxide... 

Fig. 7. Polymerization of ethylene in toluene as solvent at 80°C using Zr(allyl)Brj as initiator (9).

Polymerization of Propylene by Transition Metal Alkyl Compounds Toluene as Solvent, Temperature 65°C. Ethylene Pressure 10 atm (IS, 16)... 

In a typical run, samples (10 ml) of a reaction mixture ([M]0 = 4.44 M, [C]o = 0.03 M polymerization temperature 30°C in the dark and toluene as solvent) were withdrawn and found to contain 0.2482 gm of polymer. To this mixture was added 140 juliter of T20, activity 50 /iCi/ml, sufficient to discharge completely the color of the solution. A vigorous purification... 

The aforementioned polymer-supported bis-pyridyl ligand has also been applied in microwave-assisted asymmetric allylic alkylation [140], a key step in the enantio-selective synthesis of (R)-baclofen (Scheme 7.118), as reported by Moberg and coworkers. The ( (-enantiomer is a useful agonist of the GABAb (y-aminobutyric acid) receptor, and the racemic form is used as a muscle relaxant (antispasmodic). Under microwave heating, the enantioselectivity could be improved to 89% when using toluene as solvent (see also Scheme 6.52) [140],... 

In the reaction with BC13 or BBr3 in toluene as solvent, ionic compounds of type 51 were isolated as the main products together with the arachno-clusters 50 (X = C1, Br) and the compounds Me5C5BX2 as byproducts (Scheme 13). The nido cluster cation in 51 is identical with that in compound 48. 

Reaction of the phosphane la and the arsane 2a with freshly sublimed BuLi in the molar ratio of 1 2 in toluene as solvent at —80°C... 

In contrast, the same reaction between the bulkily substituted silyl-(fluorosilyl)phosphane le with NaN(SiMe3)2 underwent, surprisingly, a different, course (Scheme 2). Its transformation in the molar ratio of 1 1 in toluene as solvent furnished the dimer 13, whereas Id can only be completely converted to 13 if 2 molar equiv sodium amide have been employed, because of the initial formation of heteroaggregate intermediates (26). Excess of sodium amide has been recovered by... 

Another interesting class of five-membered aromatic heterocycles has recently been published by Tron et al. [54]. These compounds have biological activity in the nM range. An example of the formation of these furazan (1,2,5-oxadiazole) derivatives is shown in Scheme 9. The diol 50 was oxidized to the diketone 51 using TEMPO and sodium hypochlorite. Transformation to the bisoxime 52 was performed in an excess of hydroxylamine hydrochloride and pyridine at high temperature for several days. Basic dehydration of 52 formed two products (53a and b). A Mitsunobu reaction was then employed using toluene as solvent to form compound 53b in 24% yield. 

Another clear example is the hydrogenation of methyl-(Z)-/ -(N-acetyl)-aminocro-tonate with the Me-DuPHOS system in toluene as solvent at 20 bar hydrogen pres-... 

Other high-boiling solvents such as nitrobenzene and 2-nitrotoluene can also be used in the solvent process, but 4-nitrobiphenyl, a listed carcinogen, is produced when nitrobenzene is employed. One way to avoid the formation of substituted biphenyls is to employ a polysubstituted toluene as solvent, the substituents being chlorine or alkyl groups, mainly propyl. These are difficult to prepare but they have been patented by Toyo Inks. 

Significantly higher levels of enantioselectivity can be obtained with aromatic and unsaturated aldehydes by making use of the corresponding metal carbonyl complexes (Eq. The selectivity is higher in toluene as solvent, and the... 

An alternative method for the epoxidation of enones was developed by Jackson and coworkers in 1997 , who utilized metal peroxides that are modified by chiral ligands such as diethyl tartrate (DET), (5,5)-diphenylethanediol, (—)-ephedrine, ( )-N-methylephedrine and various simple chiral alcohols. The best results were achieved with DET as chiral inductor in toluene. In the stoichiometric version, DET and lithium tert-butyl peroxide, which was generated in situ from TBHP and n-butyllithium, were used as catalyst for the epoxidation of enones. Use of 1.1 equivalent of (-l-)-DET in toluene as solvent afforded (2/f,35 )-chalcone epoxide in 71-75% yield and 62% ee. In the substo-ichiometric method n-butyllithium was replaced by dibutylmagnesium. With this system (10 mol% Bu2Mg and 11 mol% DET), a variety of chalcone-type enones could be oxidized in moderate to good yields (36-61%) and high asymmetric induction (81-94%), giving exactly the other enantiomeric epoxide than obtained with the stoichiometric system (equation 37). 

It is worth noting that use of i-PrMgCl in ether (not in THF) and toluene as solvent for the reaction is essential for the reaction to proceed. Otherwise, the protonated product of magnesium carbenoid 78, obtained as by-product, was very difficult to separate from the desired compound (79). Interestingly, the 1,3-C,H insertion reaction is highly regioselective. 

TMTCT) in cyclohexane or toluene as solvent. The amines are powerful Li chelating agents and strongly catalyze the polymerization of polystyrylllthlum in cyclohexane by anion activation (8,25). 

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