Methylsulfinyl carbanion sulfoxide

On treatment with a strong base such as sodium hydride or sodium amide, dimethyl sulfoxide yields a proton to form the methylsulfinyl carbanion (dimsyl ion), a strongly basic reagent. Reaction of dimsyl ion with triphenylalkylphosphonium halides provides a convenient route to ylides (see Chapter 11, Section III), and with triphenylmethane the reagent affords a high concentration of triphenylmethyl carbanion. Of immediate interest, however, is the nucleophilic reaction of dimsyl ion with aldehydes, ketones, and particularly esters (//). The reaction of dimsyl ion with nonenolizable ketones and... 

A 1.5 to 2 M solution of methylsulfinyl carbanion in dimethyl sulfoxide is prepared under nitrogen as above from sodium hydride and dry dimethyl sulfoxide. An equal volume of dry tetrahydrofuran is added and the solution is cooled in an ice bath during the addition, with stirring, of the ester (0.5 equivalent for each 1 equivalent of carbanion neat if liquid, or dissolved in dry tetrahydrofuran if solid) over a period of several minutes. The ice bath is removed and stirring is continued for 30 minutes. The reaction mixture is then poured into three times its volume of water, acidified with aqueous hydrochloric acid to a pH of 3-4 (pH paper), and thoroughly extracted with chloroform. The combined extracts are washed three times with water, dried over anhydrous sodium sulfate, and evaporated to yield the jS-ketosulfoxide as a white or pale yellow crystalline solid. The crude product is triturated with cold ether or isopropyl ether and filtered to give the product in a good state of purity. 

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. 

Other carbanionic groups, such as acetylide ions, and ions derived from a-methylpyridines have also been used as nucleophiles. A particularly useful nucleophile is the methylsulfinyl carbanion (CH3SOCHJ), the conjugate base of DMSO, since the P-keto sulfoxide produced can easily be reduced to a methyl ketone (p. 549). The methylsulfonyl carbanion (CH3SO2CH2 ), the conjugate base of dimethyl sulfone, behaves similarly, and the product can be similarly reduced. Certain carboxylic esters, acyl halides, and DMF acylate 1,3-dithianes (see 10-10. )2008 Qxj(jatjye hydrolysis with NBS or NCS, a-keto aldehydes or a-... 

Aromatic nitro compounds can be methylated with dimethyloxosulfonium methylide203 or the methylsulfinyl carbanion (obtained by treatment of dimethyl sulfoxide with a strong base) 206... 

The method was used in studies of a fungal heterogalactan.150 The polysaccharide was subjected to successive tritylation, methylation, detritylation, p-toluenesulfonylation, reaction with sodium iodide, and, finally, reaction with sodium p-toluenesulfinate. The product was then treated with sodium methylsulfinyl carbanion in dimethyl sulfoxide, the product remethylated, and the polysaccharide material recovered by gel chromatography. The polymer was hydrolyzed, and the sugars in the hydrolyzate were analyzed, as the alditol acetates, by g.l.c.-m.s.1 The analysis revealed that —60% of the hexose residues that were unsubstituted at C-6 had been eliminated. As the product was still polymeric, it was concluded that these residues had constituted a part of side chains linked to a main chain of (1 — 6)-linked D-galactose residues. 

S. Hakomori, Rapid permethylation of glycolipid + polysaccharide catalyzed by methylsulfinyl carbanion in dimethyl sulfoxide, J. Biochem., 55 (1964) 1386-1388. 

Ease of nucleophilic attack at C-6 has recently been demonstrated by the virtually quantitative conversion of phenanthridine into 6-methylphenanthridine by means of methylsulfinyl carbanion in dimethyl sulfoxide.316... 

Corey and Chaykovsky described the reduction of carboxylic esters to ketones by way of / -keto sulfoxides. The ester is treated in tetrahydrofuran with a solution of methylsulfinyl carbanions in a mixture of dimethyl sulfoxide and tetrahydrofuran at 0°. This yields a j8-keto sulfoxide which is reduced with aluminum amalgam in 90% aqueous tetrahydrofuran.527 The methylsulfinyl carbanions are formed by the action of sodium hydride on dimethyl sulfoxide under nitrogen at 65-70°. 

The most important development in methylation technique is due to Hakomori, who used as the base methylsulfinyl carbanion, formed by reaction of methyl sulfoxide with sodium hydride, and thus extended to carbohydrates the reaction developed by Corey and Chaykovsky/ In certain cases, completely methylated polysaccharide may be obtained in high yield by one treatment within an hour. This method was used by Sandford and Conrad in a re-examination of the polysaccharide from Aerobacter aerogenes, and their paper should be consulted for the excellent experimental details contained therein. These authors showed that this polysaccharide has a simple, repeating structure, and previous suggestions that it is complicated and highly branched arose from interpretation based on products of incomplete methylation. 

When methylsulfinyl carbanion is added to a solution of polysaccharide in methyl sulfoxide, a gel is often formed, and methylation may be aided by ultrasonic agitation. > " ... 

Dimethylpropynylsulfoninm bromide as reactant 26, 376 Dimethyl sulfide s. under Borane Dimethylsulfinyl carbanion s. Methylsulfinyl carbanion Dimethyl sulfoxide (s. a. Methylsulfinyl carbanion)... 

Dibromobicyclo [4.1.0] heptane allowed to react at room temp, with excess sodium methylsulfinyl carbanion prepared from Na or NaH in dimethyl sulfoxide 7-bromobicyclo [4.1.0] heptane (90% trans-isomer). Y 72%. F. e. s. 

NaH stirred ca. 45 min. at 65-70° under Ng in excess dimethyl sulfoxide until Hg-evolution is complete, allowed to react with 1 equivalent of ethyl triphenyl-phosphonium bromide, then with 0.85 equivalent of benzophenone 1,1-di-phenyl-l-propene. Y 97.5%.—The reactivity of the methylsulfinyl carbanion (formed by reaction of NaH with dimethyl sulfoxide), which is even more basic than the trityl anion, is sufficient to convert phosphonium salts into ylides thereby permitting a simple and convenient modification of the Wittig reaction. E. J. Gorey and M. Ghaykowsky, Am. Soc. 8A, 866 (1962) / -diketones from carboxylic acid esters and ketones (s. Synth. Meth. 6, 737), sym. ) -diketones, s. J. J. Bloomfield, J. Org. Chem. 27, 2742 (1962). 

A soln. of dry n-propyltriphenylphosphonium bromide in dimethyl sulfoxide treated at room temp, under Ng with methylsulfinyl carbanion prepared from NaH and dimethyl sulfoxide, after 5 min. the startg. hemiacetal in dimethyl sulfoxide added, and stirred 2.5 hrs. at room temp. 2-(cf -2-pentenyl)cyclopent-3-en-l-ol. Y 70%. P.A.Grieco, J. Org. Chem. 57, 2363 (1972). 

A soln. of methylsulfinyl carbanion prepared from NaH and dry dimethyl sulfoxide according to E. J. Corey and M. Chaykovsky, Am. Soc. 87, 1345 (1965) treated at 0° under Ng with diethyl chlorophosphate, then with a soln. of 4-di-methylaminobenzaldehyde in dry dimethyl sulfoxide, and stirred 3 hrs. at room temp. / -(4-dimethylaminostyryl) methyl sulfoxide. Y 70%. J. Almog and B. A. Weissman, Synthesis 1973, 164. 

The anions of alkyl alkylthiomethyl sulfoxides have found broader application. Alkylation of the x-carbanion of methylsulfinyl(methylthio)methane with various haloalkanes and subsequent hydrolysis give aldehydes68. The use of ethylsulfinyl(ethylthio)methane leads to improved yields of alkylation products (>95%) 69. 

Most of the applications of sulfoxides in synthesis make use of the reactions of sulfur-stabilized carbanions with electrophiles [385, 386]. Thus the methylsulfinyl methylene carbanion, conveniently generated through the interaction of sodium hydride with DMSO [387], is a powerful nucleophile. 

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