Carbanion in the Generation of Ylides

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. 

Freshly distilled cyclohexanone, 10.8 g (0.11 mole), is added toO. 10mole of methylene-triphenylphosphorane, and the reaction mixture is stirred at room temperature for 30 minutes followed immediately by distillation under reduced pressure to give about 8 g (85%) of methylenecyclohexane, bp 42 (105 mm), which is collected in a cold trap. 

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