Of dimethyl sulfoxide

The widely used Moifatt-Pfltzner oxidation works with in situ formed adducts of dimethyl sulfoxide with dehydrating agents, e.g. DCC, AcjO, SO], P4O10, CCXTl] (K.E, Pfitzner, 1965 A.H. Fenselau, 1966 K.T. Joseph, 1967 J.G. Moffatt, 1971 D. Martin, 1971) or oxalyl dichloride (Swem oxidation M. Nakatsuka, 1990). A classical procedure is the Oppenauer oxidation with ketones and aluminum alkoxide catalysts (C. Djerassi, 1951 H. Lehmann, 1975). All of these reagents also oxidize secondary alcohols to ketones but do not attack C = C double bonds or activated C —H bonds. 

Find the model of dimethyl sulfoxide [(CH3)2S=0] on Learning By Modeling and exam me Its electrostatic potential map To which atom (S or O) would you expect a proton to bond d... 

Suitable strong bases include the sodium salt of dimethyl sulfoxide (m dimethyl sulfox ide as the solvent) and organohthmm reagents (m diethyl ether or tetrahydrofuran)... 

Vinyl chloride reacts with sulfides, thiols, alcohols, and oximes in basic media. Reaction with hydrated sodium sulfide [1313-82-2] in a mixture of dimethyl sulfoxide [67-68-5] (DMSO) and potassium hydroxide [1310-58-3], KOH, yields divinyl sulfide [627-51-0] and sulfur-containing heterocycles (27). Various vinyl sulfides can be obtained by reacting vinyl chloride with thiols in the presence of base (28). Vinyl ethers are produced in similar fashion, from the reaction of vinyl chloride with alcohols in the presence of a strong base (29,30). A variety of pyrroles and indoles have also been prepared by reacting vinyl chloride with different ketoximes or oximes in a mixture of DMSO and KOH (31). 

The release of dimethyl sulfoxide is accompanied by an increase in absorbance (D) at 325 nm. The absorbance D is defined as log(I(/I), where 1 and I are die intensities of die incident and transmitted light, respectively. Figure 3-15 illustrates die relationship between concentration and absorbance changes for die hydrolysis of die cobalt... 

In recent years the use of dimethyl sulfoxide (DMSO) as an oxidizing agent has found increasing application. This growing interest is undoubtedly due to the development of new methods which can be carried out under mild conditions, involve simple work-ups and give high yields of products. 

The use of dimethyl sulfoxide-acetic anhydride as a reagent for the oxidation of unhindered steroidal alcohols does not appear to be as promising due to extensive formation of by-products. However, the reagent is sufficiently reactive to oxidize the hindered 11 j -hydroxyl group to the 11-ketone in moderate yield. The use of sulfur trioxide-pyridine complex in dimethyl sulfoxide has also been reported. The results parallel those using DCC-DMSO but reaction times are much shorter and the work-up is more facile since the separation of dicyclohexylurea is not necessary. Allylic alcohols can be oxidized by this procedure without significant side reactions. 

Androst-4-ene-3,17-dione. Testosterone (0.58 g, 2 mmoles) is dissolved in a solution prepared from 3 ml of benzene, 3 ml of dimethyl sulfoxide, 0.16 ml (2 mmoles) of pyridine and 0.08 ml (1 mmole) of trifluoroacetic acid. After addition of 1.24 g (6 mmoles) of dicyclohexylcarbodiimide, the sealed reaction flask is kept overnight at room temperature. Ether (50 ml) is added followed by a solution of 0.54 g (6 mmoles) of oxalic acid in 5 ml of methanol. After gas evolution has ceased ( 30 min) 50 ml of water is added and the insoluble dicyclohexylurea is removed by filtration. The organic phase is then extracted twice with 5 % sodium bicarbonate and once with water, dried over sodium sulfate and evaporated to a crystalline residue (0.80 g) which still contains a little dicyclohexylurea. Direct crystallization from 5 ml of ethanol gives androst-4-ene-3,17-dione (0.53 g, 92%) in two crops, mp 169-170°. 

A mixture of the epoxide ca. 5 mmol), sodium azide (6 g, activated by the method of Smith) and 0.25 ml of concentrated sulfuric acid in 70 ml of dimethyl sulfoxide is heated in a flask fitted with a reflux condenser and a drierite tube on a steam bath for 30-40 hr. (Caution carry out reaction in a hood.) The dark reaction mixture is poured into 500 ml of ice water and the product may be filtered, if solid, and washed well with water or extracted with ether and washed with sodium bicarbonate and the water. The crude azido alcohols are usually recrystallized from methanol. 

In the presence of suitable a,/5-unsaturated carbonyl compounds (3) the nucleophilic methylide (2) undergoes conjugate addition followed by expulsion of dimethyl sulfoxide to give cyclopropanes (5). 

Commercial Sodium Acetylide A suspension (30 ml) of sodium acete-lide (20% in exylene) is centrifuged and the solid brown sodium acetylide is taken up in 25 ml of dimethyl sulfoxide. To this is added a solution of 5 g of 5a-hydroxy-6j5-methylandrostane-3-17,dione 3-ethylene ketal in 85 ml of dimethyl sulfoxide. After stirring at room temperature overnight, ice is added and the solution diluted to about 250 ml. The tan precipitate is collected, washed with water and dried yield 4.8 g mp 202-204°. Crystallization from ethyl acetate gives a product of mp 204-206°. 

Columns can be washed with solvents and solvent combinations suitable to remove adsorbed contaminants. When considering the adsorption of analytes, think not only of the diol functionality, but also of the adsorption to residual silanols. Often, the injection of small amounts (500 /d) of dimethyl sulfoxide removes contamination that has accumulated on the column. Aqueous solutions of sodium dodecyl sulfate, guanidine hydrochloride, or urea are compatible with Protein-Pak columns. 

Methylsulfinyl carbanion (dimsyl ion) is prepared from 0.10 mole of sodium hydride in 50 ml of dimethyl sulfoxide under a nitrogen atmosphere as described in Chapter 10, Section III. The solution is diluted by the addition of 50 ml of dry THF and a small amount (1-10 mg) of triphenylmethane is added to act as an indicator. (The red color produced by triphenylmethyl carbanion is discharged when the dimsylsodium is consumed.) Acetylene (purified as described in Chapter 14, Section I) is introduced into the system with stirring through a gas inlet tube until the formation of sodium acetylide is complete, as indicated by disappearance of the red color. The gas inlet tube is replaced by a dropping funnel and a solution of 0.10 mole of the substrate in 20 ml of dry THF is added with stirring at room temperature over a period of about 1 hour. In the case of ethynylation of carbonyl compounds (given below), the solution is then cautiously treated with 6 g (0.11 mole) of ammonium chloride. The reaction mixture is then diluted with 500 ml of water, and the aqueous solution is extracted three times with 150-ml portions of ether. The ether solution is dried (sodium sulfate), the ether is removed (rotary evaporator), and the residue is fractionally distilled under reduced pressure to yield the ethynyl alcohol. 

Primary Chlorides Dry sodium cyanide (30 g, 0.61 mole) is added to 150 ml of dimethyl sulfoxide in a flask fitted with a stirrer, reflux condenser, dropping funnel, and thermometer. The thick slurry is heated on a steam bath to 90° and the steam bath is then removed. The halide (0.5 mole of monochloride or 0.25 mole of dichloride) is slowly added to the stirred mixture, causing the temperature to increase immediately. The rate of addition should be adjusted so that the temperature of the reaction does not go above about 160°. After all the halide is added (about 10 minutes) the mixture is stirred for 10 minutes more, or until the temperature drops below 50°. In the preparation of mononitriles, the reaction mixture is then poured into water, and the product is extracted with chloroform or ether. The extract is washed several times with saturated sodium chloride solution then dried over calcium chloride, and the product is distilled. 

Secondary Chlorides With a low-boiling chloride such as 2-chlorobutane, a stirred slurry of 30 g (0.61 mole) of sodium cyanide in 150 ml of dimethyl sulfoxide is heated to 90° with a heating mantle, and 0.5 mole of the chloride is slowly added over a period of 30 minutes. The temperature of the refluxing reaction mixture slowly increases as nitrile is formed. Refluxing continues as the temperature slowly rises to 150° after 3 hours reaction time. The flask is then cooled and the reaction mixture is worked up in the same way as for the primary nitriles. With 2-chlorooctane, the sodium cyanide-dimethyl sulfoxide slurry is heated to 130° and 0.5 mole of the chloride added. The reaction mixture is maintained at 135-145° for 1 hour, then cooled, and the product is isolated as above. Examples are given in Table 16.1. 

A mixture containing 1.33 g of 5,8-dihydro-8-ethyl-2-methylthio-5-oxopyridol [2,3-d]-pyrimidine-6-carboxylic acid, 1,94 g of piperazine hexahydrate and 20 ml of dimethyl sulfoxide was heated at 110°C for 1 hour with stirring. The separated solid was collected by filtration, washed with ethanol, and then dried at Such a temperature that did not rise above 50°C to give 1,57 g of the trihydrate of the product as nearly colorless needles,... 

Water plays a crucial role in the inclusion process. Although cyclodextrin does form inclusion complexes in such nonaqueous solvents as dimethyl sulfoxide, the binding is very weak compared with that in water 13 Recently, it has been shown that the thermodynamic stabilities of some inclusion complexes in aqueous solutions decrease markedly with the addition of dimethyl sulfoxide to the solutions 14,15>. Kinetic parameters determined for inclusion reactions also revealed that the rate-determining step of the reactions is the breakdown of the water structure around a substrate molecule and/or within the cyclodextrin cavity 16,17). 

A. N-Trijluoroacetanilide. In a two-necked, round-bottomed flask fitted with a thermometer, a Drierite tube, and a magnetic stirring bar are placed 4.56 ml. (4.66 g., 0.050 mole) of aniline [Benzenamine] (Note 1) and 15 ml. of dimethyl sulfoxide (Note 2). The resulting solution is stirred and cooled in an ice water bath, and when the internal temperature has dropped to 10-15°, 21.5 g. (0.10 mole) of 1,1,1-tri-chloro -3,3,3 -trifiuoroacetone [2 -Propanone, 1,1,1 -trichloro-3,3,3-tri-fluoro-] (Note 3) is added in portions through the condenser. A mild exotherm results, and the addition is extended over ca. 5 minutes to... 

It forms a complex with 6 moles of dimethyl sulfoxide which is stable to 195°, but explds betw 200 and 235° (Ref 8)... 

FIGURE 2. The molecular model of dimethyl sulfoxide. The following C—H lengths (A), S—C—H bond angles (deg) and x(C—S—C—H) torsional angles (deg) were determined from microwave spectra by Typke17 ... 

When the third bond is formed to oxygen rather than carbon, the situation is not so simple. The formation of dimethyl sulfoxide can be pictured initially in a way analogous to the above, an empty 2sp3 orbital on oxygen being involved. The bond between sulfur and oxygen is then a coordinate bond and the structure is appropriately written as 3 or 4, with... 

Considered in this way the structure of dimethyl sulfoxide involves a double bond and a valence shell of ten electrons for sulfur (6 and 7)4,5. 

The photolysis of dimethyl sulfoxide (DMSO), as befits the parent compound in the series, has received considerable attention, both neat and in solvents like water or... 

Meissner and coworkers36 studied the pulse radiolysis of aqueous solutions of dimethyl sulfoxide. It was found that hydrated electrons react with DMSO with a rate constant of... 

Rao and Symons49 studied the formation of radicals in y-radiolysis of dilute solutions of dimethyl sulfoxide in fluorotrichloromethane. By ESR studies they found the radical cation (CH3)2SOt whose ESR spectrum show considerable g anisotropy and small methyl proton hyperfine coupling. 

As seen before, the radical cation of dimethyl sulfoxide (CH3)2SO has been detected by ESR spectroscopy among other radicals when DMSO glasses at 77 K are submitted to y-irradiation28. It has also been reported in pulse radiolysis experiments30 (Table 6). Constant current electrochemical oxidation of bis(dialkylamino)sulfoxides (R2N)2SO gives rise to radical cations which have been detected by ESR spectroscopy33. 

Ce4+ is a versatile one-electron oxidizing agent (E° = - 1.71 eV in HC10466 capable of oxidizing sulfoxides. Rao and coworkers66 have described the oxidation of dimethyl sulfoxide to dimethyl sulfone by Ce4+ cation in perchloric acid and proposed a SET mechanism. In the first step DMSO rapidly replaces a molecule of water in the coordination sphere of the metal (Ce v has a coordination number of 8). An intramolecular electron transfer leads to the production of a cation which is subsequently converted into sulfone by reaction with water. The formation of radicals was confirmed by polymerization of acrylonitrile added to the medium. We have written a plausible mechanism for the process (Scheme 8), but there is no compelling experimental data concerning the inner versus outer sphere character of the reaction between HzO and the radical cation of DMSO. 

B. Benzocyclopropene. A dry, three-necked, round-bottomed flask fitted with a sealed mechanical stirrer, a reflux condenser, and a pressure-equalizing dropping funnel is flushed with nitrogen. To the flask is added 35.0 g (0.312 mole) of potassium ferf-butoxide (Note 1), followed by 200 ml. of dimethyl sulfoxide (Note 5). The stirred mixture is cooled to 15-20° (Note 6) with an ice bath and 24.5 g. 

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