Sulfoxide, dimethyl anion

Some 30 years later, Wanzlick s work was reinvestigated by Arduengo et al., who were able to prepare and to isolate the imidazol-2-ylidene IVc (R = adamantyl) in near quantitative yield (Scheme 8.4). The deprotonation of the 1,3-di-l-adamantylimidazolium chloride (4c) was carried out with sodium or potassium hydride, in the presence of catalytic amounts of either f-BuOK or the dimethyl sulfoxide (DMSO) anion. Carbene IVc is thermally stable in the solid state (colorless crystals, mp 240-241 °C). 

For a cationic (CTABr) and an anionic (NaLS) surfactant in a variety of dipolar aprotic solvents, e.g., dimethyl sulfoxide, dimethyl formamide, the variation of conductance with surfactant concentration is characteristic of micellization, and critical micelle concentrations were reported, which tend to be higher than those in water, especially for CTABr [144]. 

The formation of the above anions ("enolate type) depend on equilibria between the carbon compounds, the base, and the solvent. To ensure a substantial concentration of the anionic synthons in solution the pA" of both the conjugated acid of the base and of the solvent must be higher than the pAT -value of the carbon compound. Alkali hydroxides in water (p/T, 16), alkoxides in the corresponding alcohols (pAT, 20), sodium amide in liquid ammonia (pATj 35), dimsyl sodium in dimethyl sulfoxide (pAT, = 35), sodium hydride, lithium amides, or lithium alkyls in ether or hydrocarbon solvents (pAT, > 40) are common combinations used in synthesis. Sometimes the bases (e.g. methoxides, amides, lithium alkyls) react as nucleophiles, in other words they do not abstract a proton, but their anion undergoes addition and substitution reactions with the carbon compound. If such is the case, sterically hindered bases are employed. A few examples are given below (H.O. House, 1972 I. Kuwajima, 1976). 

Solvent variation can gready affect the acidity of hydantoins. Although two different standard states are employed for the piC scale and therefore care must be exercised when comparing absolute acidity constants measured in water and other solvents like dimethyl sulfoxide (DMSO), the huge difference in piC values, eg, 9.0 in water and 15.0 in DMSO (12) in the case of hydantoin itself, indicates that water provides a better stabilization for the hydantoin anion and hence an increased acidity when compared to DMSO. 

A AlI lation. 1-Substitution is favored when the indole ring is deprotonated and the reaction medium promotes the nucleophilicity of the resulting indole anion. Conditions which typically result in A/-alkylation are generation of the sodium salt by sodium amide in Hquid ammonia, use of sodium hydride or a similar strong base in /V, /V- dim ethyl form am i de or dimethyl sulfoxide, or the use of phase-transfer conditions. 

Chemiluminescence is also obtained by anionic autooxidation of (41) with oxygen ia alkaline dimethyl sulfoxide (DMSO) (216). Qc has been reported to be 10% and ketone (43) and CO2 are obtained. Several analogues of luciferin have been prepared that are also chemiluminescent when they react with oxygen ia alkaline DMSO (62). 

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). 

This ester is converted in high yield to the y -ketosulfoxide by means of the dimethyl sulfoxide anion. Heating in acetic acid then produces a hemi-mercaptal acetate, which on treatment with Raney nickel gives the desired 21-acetoxy-20-ketone in a 50-70% overall yield from the -ketosulfoxide. A 17a-hydroxyl may also be present during the sequence. 

The addition of the anion of the 1,3-dimethyl-2-butenyl sulfoxides to 2-cyclopentenone was examined2. The anion of rar-2-methyl-4-(phenylsulfinyl)-2-pentene gave a 50 50 mixture of ( )- and (Z)-y-1,4-adducts which differed in the relative configuration of the new stereocenter regarding the stereocenter at sulfur. That is, for either the (Z)- or the ( )-product there is complete asymmetric induction from the stereocenter at sulfur, but in the opposite direction. When the rm-butyl analog, ruc-4-(/wt-butylsulfinyl)-2-methyl-2-pcntcne, was reacted, it gave exclusively the ( )-adduct, likewise as a single diastereomer. 

Novi and coworkers124 have shown that the reaction of 2,3-bis(phenylsulfonyl)-l,4-dimethylbenzene with sodium benzenethiolate in dimethyl sulfoxide yields a mixture of substitution, cyclization and reduction products when subjected at room temperature to photostimulation by a sunlamp. These authors proposed a double chain mechanism (Scheme 17) to explain the observed products. This mechanism is supported by a set of carefully designed experiments125. The addition of PhSH, a good hydrogen atom donor, increases the percent of reduction products. When the substitution process can effectively compete with the two other processes, the increase in the relative yield of substitution (e.g., with five molar equivalents of benzenethiolate) parallels the decrease in those of both cyclization and reduction products. This suggests a common intermediate leading to the three different products. This intermediate could either be the radical anion formed by electron transfer to 2,3-bis(phenylsulfonyl)-l,4-dimethylbenzene or the a radical formed... 

Dccalin (decahydronaphthalene),benzene, 1,4-dioxane, and ethanol may be used as solvents for the photolysis. In an alternative procedure, volatile materials swept from the photolysis vessel are condensed in a dry ice trap. This cold mixture is added to a flask containing a magnetically stirred solution of dimsyl anion in dimethyl sulfoxide, and fractionation at reduced pressure provides a solution of bicyclopentene in tetrahydrofuran. 

This procedure, which involves the addition of an anion derived from a nitrile to an unactivated acetylenic bond under rather mild conditions, is a convenient general method for the synthesis of a-vinyl-nitriles (see Table I). The reaction proceeds smoothly in either dimethyl sulfoxide or hexamethylphosphoric triamide (see p. 103 for warning) as solvent with a tetraalkylam monium salt as catalyst. The products thus prepared are obtained in yields higher2 than those obtained under conventional conditions, which generally require higher temperatures and elevated pressures.3-4... 

When electron-withdrawing groups are attached to the double bond, the reaction is strongly inhibited and may fail completely. In such cases, the bromide anion, produced by the reaction of dimethyl sulfoxide with N-bromosuccinimide, competes with the dimethyl sulfoxide for the bromonium (or bromo carbonium) ion, an intermediate of the reaction. Thus, dibromide may accompany recovered alkene or any bromohydrin formed. Similarly, exogenous anions often compete with dimethyl sulfoxide for the cation. ... 

THF, tetrahydrofuran DMF, dimethylformamide DMSO, dimethyl sulfoxide DPSO, diphenyl sulfoxide en, ethylenediamine py, pyridine pic, picoline lut, lutidine nic, nicotinamide IMD, imidazole MelMD, N-methylimidazole 1-Cl-nap, 1-chloronaph-thyl acac, acetylacetonyl anion, CH3COCHCOCH3 C4H9O3, acetoacetic ester anion, CH3COCHCOOC2HS C4H,oN2, piperazine C7HSN2, benzimidazole. 

Dimsyl anion 88 is known to add to styrene, and to 1,1-diphenylethylene in the presence of a base, forming 3-arylpropyl methyl sulfoxides . Treatment of ( )-3,3-dimethylthiacyclo-oct-4-ene-l-oxide 89 with n-BuLi gave exo-4,4-dimethyl-2-thiacyclo-[3.3.0]octane 2-oxide 90, a bicyclic addition product of the internal double bond. A similar cyclization was observed in the reaction of 91 with n-BuLi. ... 

ESR experiments employing in situ photolytic decomposition of the peroxydisulfate anion (S20g ) have been carried out to study the reaction of S04 with aliphatic sulfoxides. In the case of dimethyl sulfoxide three radicals are detected ( CHj, CH3 S02, CH2 S(0)CH3), the proportion being pH-dependent. The reaction is assumed to proceed via an initially formed radical cation (not detected) which would be rapidly hydrated to give an intermediate identical with that generated by OH addition on the sulfoxide. Such a process parallels the rapid hydration of radical cations formed from thiophene in their reactions with SO/ and... 

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