Dimethyl sulfoxide, as solvent

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... 

Bajugam and Flitsch [217] have described the synthesis of glycosylamines from mono-, di-, and trisaccharides by direct microwave-assisted Kochetkov amination (Scheme 6.110). The reaction was found to be effective with just a fivefold excess (w/w) of ammonium carbonate with respect to the sugar, as compared to the 40-or 50-fold excess needed under thermal conditions. All transformations were completed within 90 min in dimethyl sulfoxide as solvent, maintaining the vessel temperature at an apparent 40 °C using the heating-while-cooling technique (see Section 2.5.3). 

Moore S (1968) Amino acid analysis aqueous dimethyl sulfoxide as solvent for the... 

In addition, the reduction of a-11 and (3-11 was s tudied in dimethyl sulfoxide as solvent, in the presence of pyridiniump-toluensulfonate. This medium makes mutarota-tion slower than the redox process.73 The two anomeric forms could reduce Cr(VI) and Cr(V) by formation of a Cr(VI) and Cr(V) ester intermediate. The equilibrium constant for this step and the rate of the redox step were different for each anomer for a-11, the equilibrium constant for ester formation is higher than for (3-11, but the redox process within this complex is faster for the latter anomer. These differences can be explained by the better chelating capacity of the 1,2-cri-diol moiety of a-11. Room-temperature CW-EPR spectra of these mixtures revealed for the a anomer several five-coordinated Cr(V)-bischelates (giso= 1.9820 [crilso 15.9xl(r4cm 1 (=47.7MHz)],... 

The lithiation-substituton methodology was further extended for meso-functionalization of other bis(furan-2-yl)methane 263, using n-BuLi and dimethyl sulfoxide as solvent additives (Scheme 102). The approach was also extended for C-5 functionalization of bis(furan-2-yl)methane (08TL6234). 

A further instructive study on the influence of protic and dipolar aprotic solvents on the rate of SnI heterolysis of tertiary R3C-X (with X = Cl, Br, I, 2,4-dinitrophenolate) shows that the rate-accelerating anion solvation due to H-bonding by protic solvents decreases dramatically on increasing the radius of the halide ions. Therefore, the differential solvation transferred from anion-solvating methanol to cation-solvating dimethyl sulfoxide as solvent is reversed on going from the chloro- to the iodoalkane at 60 °C /ji(DMSO)/ki(MeOH) = 0.05 (t-BuCl) < 0.57 (t-BuBr) < 6.9 (t-BuI) the 2,4-dinitrophenolate ion behaves like the iodide [830]. 

Sinee the Cope elimination reaetion of amine oxides proeeeds with intramoleeular proton abstraction by the A -oxide group aeeording to Eq. (5-122), it is not surprising that with dimethyl sulfoxide as solvent the reaetion oeeurs at room temperature [328, 331]. Pro tie solvents require temperatures of 120 to 150 °C beeause hydrogen bonding of the oxygen terminal makes the reaetion more diffieult. 

Dimethoxyethane is preferred to dimethyl sulfoxide as solvent for the formyl-ation of ketones with carbon monoxide in the presence of an alkali metal alkoxide. This is due to the fact that DMSO is slightly protic in the presence of a strong base (potassium t-butoxide) and hence not inert. 

Fluorinated aromatic compounds. Finger and Kruse found that an aromatic chlorine or bromine atom activated by an o- or p-nitro group is subject to nucleophilic displacement by fluoride ipn on reaction with potassium fluoride in solvents such as succinonitrile, dimethyl formamide, or dimethyl sulfoxide. Unpublished work at Olin Mathieson Chemical Corporation indicates that best results are obtained with dimethyl sulfoxide as solvent and with potassium fluoride that has been finely ground (<100 mesh) and dried in a vacuum oven at 100° for at least 4 hrs. prior to use. In a typical case a mixture of p-nitrochlorobenzene, potassium fluoride, and dimethyl sulfoxide is stirred under reflux at 180° for 8-9 hrs., the cooled mixture... 

Thermal decomposition. The usual procedure for cari ying out a Wolff-Kishner reduction is to heat a hydrazone with base to a temperature of 200°. Cram e( ai. reported the striking finding that with dimethyl sulfoxide as solvent and potassium r-butoxide as base the reaction can be conducted at room temperature. For example,... 

Cyclopropyl thioacetals are conveniently prepared by treating 1,1-dichlorocyclopropanes with a thiol under basic conditions using methanol, ethanol or dimethyl sulfoxide as solvent. Almost all the thioacetals synthesized this way are l,l-bis(phenylsulfanyl)cyclopropanes. The reaction... 

Using dimethyl sulfoxide as solvent leads to excellent results even secondary halides give yields of up to 80% therein,435 as shown in the following case ... 

Dimethylpropyl group, 66 Dimethyl sulfate, 596 Dimethyl sulfide, 241 Dimethyl sulfoxide as solvent... 

In this context our interest was focused on sulfonic acid esters of starch, derived fh)m the reaction of organic sulfonyl chloride (e.g. benzene, methane, or toluene sulfonyl chloride). These derivatives can be employed as partially protected and reactive intermediates. Up to now, especially the reaction of starch with p-toluenesulfonyl chloride in pyridine was studied, i.e. under heterogeneous reaction conditions, which may be accompanied by several side reactions. Alternatively, a homogeneous procedure was published using dimethyl sulfoxide as solvent for starch. However, the sulphur contents of the products were very low and an extensive degradation of the polymer occured . The extent of / toluenesulfonyIation of primary and secondary groups was determined by the iodination method. It was revealed that the reaction proceeds faster at 0-6 than at 0-2 and 0-2... 

The quaternized polymers exhibit an outstanding solubility in polar aprotic solvents. Therefore, flexible and tough membranes varying ionic content could be prepared by solution casting using dimethyl sulfoxide as solvent. The membranes have a high ionic conductivity and excellent chemical stability [113]. 

Satisfactory dissolution of the starch at atmospheric pressure is difficult to achieve and a thermostable a-amylase is often included. Pressure cooking with an autoclave at 130°C is better, but such equipment is uncommon in laboratories. Dimethyl sulfoxide, with 10% water included, is an excellent solvent for starch, but this water content is critical, and the organic solvent is present during the subsequent enzyme hydrolysis. However, commercial kits are available that employ dimethyl sulfoxide as solvent. Acid may also be used for dissolution but, if a large amount is used, care must be taken that the starch does not salt-out on neutrafization. A most convenient solvent has proved to be cold dilute sodium hydroxide solution. The starch, 250 mg, is slurried in 25 ml of water, an equal volume of 1 moll sodium hydroxide is added and stirring is continued for 5 min. Before addition of enzymes the solution is adjusted to pH 4.5-5.0 with acetic acid. 

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