Methylsulphinyl carbanion

It has been found that aryl groups can also be introduced into the a-position of sulphoxides. Corey and Chaykovsky have demonstrated that chlorobenzene reacts at room temperature with an excess of sodium methylsulphinyl carbanion to give methyl benzyl sulphoxide in 41% yield. The authors believe that a benzyne intermediate may be involved in the reaction400,401 (equation 174). 

Reductive cyclization of the nitroarylethylisoquinolines (40 R = H) and (40 R = Me) with triethylphosphite gave the benzimidazoisoquinoline benzacridine (42) respectively (Scheme 5). These products were each synthesized by independent routes. The formation of (42) is analogous to the formation of a benzocarbazole from 6-nitrolaudanosine (c/. Vol. 1). The reactions of various bromaralkylisoquinolines with methylsulphinyl carbanion are described in Section 7. 

The reaction of benzo[f]quinoline with methylsulphinyl carbanion prepared from dimetl lsulphoxide and sodium hydride leads to the 5-methyl and the 6-methyl derivatives in a 1 4 ratio. Although benzo[flquinoline-4-oxide gives a high yield of phenanthrene under these conditions, the carbanion generated using potassium t-butoxide as the base leads to alkylation at C-3 and to simultaneous deoxygenation (Y. Hamada and I. Takeuchi. J. org. Chem.. 1977. fa, 4209). 

The sodium salt of the methylsulphinyl carbanion, Me SO CH2 Na+, has simple uses in synthesis, such as converting alcohols into alkoxides, for the synthesis of ethers by alkylation with an alkyl halide, or for synthesis of xanthates by successive treatment with CSa and an alkyl halide. The method is useful for reactions with tertiary alcohols. 

The chemistry of the methylsulphinyl carbanion, MeS(0)=CHa, has been reviewed by Durst and by Field. Szmant has briefly reviewed the stereochemistry of sulphinyl carbanions. Martin has reported the isolation of etherate complexes of dimsyl-lithium but reported the uncomplexed material to be shock-sensitive. 

The sjmthesis of (+)-chanoclavin I (582) has been achieved by a multistage route from the acetal (580) by way of the key intermediate (581) whose aliphatic double bond is readily cleaved by ozone. A third, convenient synthesis of the diterpenoid trachylo-bane (586) has been achieved by a reductive homoallylic cyclization. Reaction of the mesylate ester (583) with methylsulphinyl carbanion gives the ketone (584) and the alcohol (585). Oxidation of the crude product mixture with Jones reagent gave ketone (584) which can be reduced to trachylobane (586). ... 

Use of the methylsulphinyl carbanion as base is recommended for the synthesis of ethers from alcohols and alkyl halides. The catalysed formation of dimethyl ether from hydrogen and carbon dioxide has been reported. Carey has described the use of the silicon-modified organolithium reagent (73) in the preparation of vinyl thioethers (Scheme 151). In order to extend the scope of this reaction to include vinyl ethers themselves, an attempt was made to metalate trimethylsilylmethyl ether use of n-buty 1-lithium resulted in nucleophilic attack on silicon, whereas t-butyl-lithium abstracted the wrong proton, as shown in Scheme 151. 

Conversion of terminal olefins into alk-l-ynes by a bromination-dehydro-bromination sequence is often easier in theory than in practice. The use of DMSO as solvent and methylsulphinyl carbanion or sodamide as the base gives excellent yields with little isomerization to alk-2-ynes. Moreover, conditions have also been found for transformation of alk-l-ynes into alk-2-ynes. ... 

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