Dimethylsulfoxide carbanion reactions

Treatment of dimethylsulfoxide (DMSO) with sodium hydride generates methylsulfinyl carbanion (dimsyl ion), which acts as an efficient base in the production of ylides. The Wittig reaction appears to proceed more readily in the DMSO solvent, and yields are generally improved over the reaction with -butyl lithium (i). Examples of this modification are given. 

The enolate ions from acyclic and cyclic aliphatic ketones, and mainly those derived from acetone and pinacolone, are the carbanions most extensively studied so far. In general, the substitution products are obtained in good yield under irradiation in both liquid ammonia and dimethylsulfoxide (DMSO). For example, the anti-inflammatory drug fluorobiprophen 1 can be synthesized by the reaction of... 

Oxaspiropentanes have been obtained from the cyclopropylide 103, prepared by treatment of cyclopropyldiphenylsulfonium tetrafluoroborate 102 either with sodium methylsulfmyl carbanion in dimethoxyethane at —45 °C or with potassium hydroxide in dimethylsulfoxide at 25 °C. While the reaction of the ylide 103 with a,p-unsaturated carbonyl compounds has resulted in selective cyclopropylidene transfer to the a, 3-carbon-carbon double bond leading to spiropentanes, condensation of 103 with non-conjugated aldehydes and ketones led to oxaspiropentanes such as 104, which have been isolated in 59-100% yields, Eq. (30) 57). 

Methylation. The reaction of 1,10-phenanthroline-JV-oxide with methylsulfinyl carbanion has been reported. Liberation of the A oxide moiety occurred when the compound was treated with sodium hydride in dimethylsulfoxide for 0.5 h, resulting in the formation of benzo[A]quinoline as a sole product in 48% yield. Prolonging the reaction time to 4 h led to a mixture of three products corresponding to further methylation at the 5- and 6-positions of the quinoline ring (eq 4). ... 

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