Methyl sulfoxide as solvent

NRRL B-742 dextran may be artifactual structures, resulting from incomplete methylation of this highly branched polysaccharide. Dextrans have been methylated most frequently by the Haworth method, " and by procedures that employ sodium and methyl iodide in liquid ammonia. " " Rapid methylation of dextrans has been achieved " through the use of the Hakomori procedure, which utilizes methyl sulfoxide as solvent for the dextran. Careful control of the reaction temperature would, however, appear to be essential when a dextran is methylated in this solvent, as hot methyl sulfoxide has been reported to depolymerize native dextrans." ... 

Similarly sodium methoxide (NaOCHj) is a suitable base and is used m methyl alco hoi Potassium hydroxide m ethyl alcohol is another base-solvent combination often employed m the dehydrohalogenation of alkyl halides Potassium tert butoxide [K0C(CH3)3] is the preferred base when the alkyl halide is primary it is used m either tert butyl alcohol or dimethyl sulfoxide as solvent... 

Before concentration, acid hydrolyzates are neutralized, most commonly with barium carbonate, although such organic bases as methyldioctylamine has been used.81 This step normally causes little loss, except by adsorption on, for example, barium sulfate,82 but the following points are of interest. Neutralization with ammonia has been recommended,83 as the neutral solution may be evaporated directly to dryness without filtration, and the ammonium sulfate formed is insoluble in methyl sulfoxide, a solvent used for trimethyl-silylation. The authors83 also found that, when hydrolyzates are neutralized with ion-exchange resins, the pH of the concentrated solutions may differ by as much as 2 units of pH. D-Fructose has been found to be epimerized by barium carbonate or pyridine, and lead... 

One of the more important applications of methyl sulfoxide as a sugar solvent is for n.m.r. spectral studies, where, in conjunction with acetone-de, it has been used because exchange reactions are suppressed191 (see the n.m.r. section, p. 124). Methyl sulfoxide dissolves both amylose and amylopectin,192 and these can then be separated by the judicious use of co-solvents after dissolution.193 Ultracentri-... 

The use of methyl sulfoxide as the solvent and boron trifluoride etherate as the catalyst has been explored,29 and has given good yields of acetals from aldehydes (but not ketones). The procedure does suffer from certain disadvantages, in particular, the laborious removal of the solvent by vacuum distillation, and the fact that some anomerization may result when glycosides are so treated. 

With the combination of dimethyl sulfoxide as solvent and NaH as base, di-alkylated derivatives in yields superior to those previously found can be obtained from malononitrile and 2,4-pentanedione with methyl iodide, butyl bromide, or benzyl chloride. Reaction conditions are mild and reaction times short.— E A soln. of malononitrile in dimethyl sulfoxide added during 15 min. to a stirred slurry of NaH in the same solvent, stirring continued 15 min. with occasional cooling, then benzyl chloride added during 20 min. with occasional cooling, and stirred 8.5 hrs. at room temp. dibenzylmalonitrile. Y 64.5-75.9%. F. e. s. J. J. Bloomfield, J. Org. Ghem. 26, 4112 (1961). 

The relative ease of H/D exchange of the methylene protons of benzyl methyl sulfoxide is markedly influenced by the nature of the base and the solvent used, as shown in Table 12. The data reveal that rather high stereoselectivities can be observed when alkyllithium-THF is used. 

For the addition of ethylene, EtOAc as solvent was particularly advantageous and gave 418 in 60% yield (Scheme 6.86). The monosubstituted ethylenes 1-hexene, vinylcyclohexane, allyltrimethylsilane, allyl alcohol, ethyl vinyl ether, vinyl acetate and N-vinyl-2-pyrrolidone furnished [2 + 2]-cycloadducts of the type 419 in yields of 54—100%. Mixtures of [2 + 2]-cycloadducts of the types 419 and 420 were formed with vinylcyclopropane, styrene and derivatives substituted at the phenyl group, acrylonitrile, methyl acrylate and phenyl vinyl thioether (yields of 56-76%), in which the diastereomers 419 predominated up to a ratio of 2.5 1 except in the case of the styrenes, where this ratio was 1 1. The Hammett p value for the addition of the styrenes to 417 turned out to be -0.54, suggesting that there is little charge separation in the transition state [155]. In the case of 6, the p value was determined as +0.79 (see Section 6.3.1) and indicates a slight polarization in the opposite direction. This astounding variety of substrates for 417 is contrasted by only a few monosubstituted ethylenes whose addition products with 417 could not be observed or were formed in only small amounts phenyl vinyl ether, vinyl bromide, (perfluorobutyl)-ethylene, phenyl vinyl sulfoxide and sulfone, methyl vinyl ketone and the vinylpyri-dines. 

Figure 3. Effect of temperature on the magnitude of the chemical shift difference between isopropyl methyl sulfoxide enantiomers in the presence of (-)-TFPE in CCI4. Molar ratio of alcohol to sulfoxide to solvent is 2 1 5. Symbols are as in Figure 2. Reprinted with permission from Tetrahedron Lett. 1974,2295-2298.

Bell, 1989 Rhee and Bell, 1991), random copolymers of methyl acrylate and acrylonitrile were directly polymerized onto the carbon fiber surface. Dimethyl formamide, dimethyl sulfoxide and distilled water proved to be useful as solvents for this process. Polymerization can take place on the carbon fiber electrode, with initial wetting of the fiber surface leading to better adhesion of the polymer formed. The structure and properties of the polymer can be varied by employing different vinyl and cyclic monomers in homopolymerization. Chemical bond can also be formed, such as polymer grafting to the carbon fiber surface. 

Solvents that have been less extensively used are N-methyl-2-pyrrolidinone and hexamethylphosphoric triamide.183 The author of this article183 also discussed the purification of chlorotrimethylsilane, and the anomalous results that may be obtained from the use of impure reagent have been commented on in the case of analyses of pentaerythritol.184 The various methods available for the bulk purification of methyl sulfoxide have been reviewed,185 and a symposium on this compound reviewed its use as a solvent in selected reactions.186... 

Analogous methyl azidoformate forms with norbornene a thermal unstable triazoline.251 The decomposition products are 40% aziridine and 55% imide. Furthermore it has been observed that the rate of nitrogen evolution of the triazoline from methyl azidoformate increases threefold when triglyme and 20-fold when dimethyl sulfoxide are substituted for 1,1-diphenylethane as solvents. This fact supports a betaine intermediate in the thermal decomposition reaction. The triazoline from 2,4-dinitrophenyl azide and norbornene could just be isolated, but from picryl azide only the aziridine was obtained.252-254 Nevertheless, the high negative value of the activation entropy (—33.4 eu) indicates a similar cyclic transition state for both reactions. 

Methyl sulfoxide has been used, chiefly by Micheel and his coworkers, as an effective solvent for the acid-catalyzed polycondensation of sugars.93-101 In view of the good yields of material of high molecular weight, the methods developed offered considerable promise. Unfortunately, it was subsequently found 4 that, in acidic media, methyl sulfoxide undergoes a... 

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