Dimethyl sulfoxide aprotic, polar

A mixture of 6a-bromo-7-oxototarol, NaHCOg, and dimethyl sulfoxide as polar aprotic solvent heated 1.5 hrs. at 120° 7-oxo-5,10-secototara-5,8,10(20),11,13-... 

Phenylacetonitrile added to a suspension of Na-tert-butoxide in dimethyl sulfoxide as polar aprotic solvent, phenyl isothiocyanate added dropwise below 25°, and stirred 1 hr. at 20° phenylcyanothioacetanilide. Y 81%. F. e. s. M. Pesson, S. Geiger, and Y. Person, C. r. 266 (C), 1555 (1968) dimethyl sulfoxide in organic synthesis, review, s. T. Durst, Adv. Org. Chem. 6, 285 (1969). 

Oxidation of Sulfides (Section 11.12C) Oxidation of a sulfide gives either a sulfoxide or a sulfone, depending on the oxidizing agent and experimental conditions. Air oxidation of dimethyl sulfide is a commercial route to dimethyl sulfoxide, a polar aprotic solvent. 

The preparation of fluoroaromatics by the reaction of KF with perhaloaromatics, primarily hexachloroben2ene, has received considerable attention. Two methods were developed and include either the use of an aprotic, polar solvent, such as /V-methy1pyrro1idinone (8), or no solvent (9). These methods plus findings that various fluoroaryl derivatives are effective fungicides (10) prompted development of a commercial process for the production of polyfluoroben2enes (11). The process uses a mixture of sodium and potassium fluorides or potassium fluoride alone in aprotic, polar solvents such as dimethyl sulfoxide or sulfolane. 

Solvent for Displacement Reactions. As the most polar of the common aprotic solvents, DMSO is a favored solvent for displacement reactions because of its high dielectric constant and because anions are less solvated in it (87). Rates for these reactions are sometimes a thousand times faster in DMSO than in alcohols. Suitable nucleophiles include acetyUde ion, alkoxide ion, hydroxide ion, azide ion, carbanions, carboxylate ions, cyanide ion, hahde ions, mercaptide ions, phenoxide ions, nitrite ions, and thiocyanate ions (31). Rates of displacement by amides or amines are also greater in DMSO than in alcohol or aqueous solutions. Dimethyl sulfoxide is used as the reaction solvent in the manufacture of high performance, polyaryl ether polymers by reaction of bis(4,4 -chlorophenyl) sulfone with the disodium salts of dihydroxyphenols, eg, bisphenol A or 4,4 -sulfonylbisphenol (88). These and related reactions are made more economical by efficient recycling of DMSO (89). Nucleophilic displacement of activated aromatic nitro groups with aryloxy anion in DMSO is a versatile and useful reaction for the synthesis of aromatic ethers and polyethers (90). 

It is prepared from the polycondensation of the disodium salt of bisphenol A and 4,4-dichlorodiphenyl sulfone in a polar aprotic solvent such as dimethyl sulfoxide (26). 

Dimethyl sulfoxide (DMSO) is a particularly well-known sulfoxide that is often used as a polar aprotic solvent. It must be handled with care, however, because it has a remarkable ability to penetrate the skin, carrying along whatever is dissolved in it. 

Polar aprotic solvent (Section 11.3) A polar solvent that can t function as a hydrogen ion donor. Polar aprotic solvents such as dimethyl sulfoxide (DMSO) and dimethyl-formamide (DMF) are particularly useful in Sn2 reactions because of their ability to solvate cations. 

The rate of alkylation of enolate ions is strongly dependent on the solvent in which the reaction is carried out.41 The relative rates of reaction of the sodium enolate of diethyl n-butylmalonate with n-butyl bromide are shown in Table 1.3. Dimethyl sulfoxide (DMSO) and iV,Ai-dimethylformamide (DMF) are particularly effective in enhancing the reactivity of enolate ions. Both of these are polar aprotic solvents. Other... 

The practically complete discrimination of acetonitrile in favor of dimethyl sulfoxide (Entry 14) is also remarkable since both solvents are of the same category (dipolar aprotic) and, in addition, they have comparable polarities 34). These facts are retained even when acetonitrile is of tenfold e.xcess in a respective mixture with dimethyl... 

This type of charge reduction by charge transfer to the solvent molecule occurs in general when SI are polar solvent molecules of aprotic character such as dimethyl-sulfoxide, dimethyl formamide, and acetonitrile. Protic solvents such as water lead to charge reduction which involves an intracluster proton transfer reaction ... 

Aromatic nucleophilic radiofluorinations are usually performed in aprotic polar solvents, such as dimethyl sulfoxide (DMSO), sulfolane or dimethylacetamide, and often under basic conditions (because of the presence of Kryptofix-222 / potassium carbonate). Completion of the p F]fluoride incorporation often requires moderate to high temperatures (100-170 °C) for 10-30 min. Microwave technology can be a successful application here, resulting in improved yields and shorter reaction times [29,170-173],... 

The classical synthetic pathway to prepare polyimides consists of a two-step scheme in which the first step involves polymerization of a soluble and thus processable poly(amic acid) intermediate, followed by a second dehydration step of this prepolymer to yield the final polyimide. This preparative pathway is representative of most of the early aromatic polyimide work and remains the most practical and widely utilized method of polyimide preparation to date. As illustrated in Scheme 4, this approach is based on the reaction of a suitable diamine with a dianhydride in a polar, aprotic solvent such as dimethyl sulfoxide (DMSO), dimethylacetamide (DMAc), dimethylformamide (DMF), or AT-methylpyrrolidone (NMP), generally at ambient temperature, to yield a poly(amic acid). The poly(amic acid) is then cyclized either thermally or chemically in a subsequent step to produce the desired polyimide. This second step will be discussed in more detail in the imidization characteristics section. More specifically, step 1 in the classical two-step synthesis of polyimides... 

When C—H bond formation occurs, the result is inversion. Racemization results in polar aprotic solvents such as dimethyl sulfoxide. In these solvents the carbanions are relatively long-lived (because the solvent has no proton to donate) and symmetrically solvated. 

Silyl enol ethers can be dimerized to symmetrical 1,4-diketones by treatment with Ag20 in dimethyl sulfoxide or certain other polar aprotic solvents.465 The reaction has been performed with R2, R-1 = hydrogen or alkyl, though best yields are obtained when R2 = R1 = H. In certain cases, unsymmetrical 1,4-diketones have been prepared by using a mixture of two silyl enol ethers. Other reagents that have been used to achieve either symmetrical or cross-coupled products are iodosobenzene-BFy-EtiO.466 ceric ammonium nitrate,467 and lead tetraacetate.m If R1 = OR (in which case the substrate is a ketene silyl acetal), dimerization with TiCL, leads to a dialkyl succinate (32, R1 = OR).4 9... 

Further improvements in dehalogenation selectivity and yields can be achieved by using dipolar aprotic solvents. Dimethylformamide has mostly been used for this purpose,18,56,84 97 although dimethyl sulfoxide,98,99 especially when combined with sonication at room temperature (vide infra), deserves attention in particular cases.100,101 Other polar and dipolar aprotic solvents have also been used, namely, acetone,4 butan-2-one,4 acetonitrile,102 acetic anhydride,103104 ethyl acetate,61 tetrahydrothiophene 1,1-dioxide (sulfolane)105 and hexamethyl-phosphoric triamide,106 but no details were reported on their advantages over dimelhylform-amide or dimethyl sulfoxide. Better performance of dipolar aprotic solvents, such as dimethyl-formamide, over other solvents has been demonstrated in the recent comparison of the dehalogenation of 4,5-dichloro-4,5,5-trifluoropentan-l-ol (4) with zinc in various solvents.90... 

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