Dimethylsulfinyl carbanion

Morrow et al. applied this reaction to the synthesis of the steroidal spiroazirine (29) and discovered that higher yields can be achieved if the dimethylsulfinyl carbanion is substituted for sodium isopro-poxide as the base.15,16 Unfortunately, this method lacks generality. 

The use of potassium f-butoxide as the base directly produced a low yield of 1-azirine contaminated with propiophenone. However, Nair has reported that azirine (37) can be prepared from hydrazone (34) in 63% yield by using the dimethylsulfinyl carbanion as the base.18... 

Phenyl-l-azirine (42a) reacts with acetophenone in the presence of the dimethylsulfinyl carbanion to give 2,4-diphenylpyrrole (150).65 This reaction probably involves initial attack of the enolate anion on the carbon-nitrogen double dond, to give intermediate 147 and 148 which ring-opens to 149 and loses hydroxide ion giving pyrrole (150). A similar reaction of ethyl benzoylacetate with 2-phenyl-l-azirine yields 3-benzoyl-4-phenyl-2-oxopyrroline (151). 

Recently Klein and Hauser 84> used the dimethylsulfinyl carbanion to convert 6 to 7 in 81—85% yield. This method is far more convenient for the synthesis of 7 than the sodium amide method, for the yield is comparable and the reaction can be carried out at room temperature. Lepley and Brodof 97> reported another method of preparing 7 in good yield. Their technique consisted of treating the ether soluble p-(tert-butyl)-phenoxide salt of 6 with butyllithium at low temperature (0—15 °C). An 88—92% yield of 7 was obtained under these conditions. At higher temperatures, however, the amount of 8 increases with decreasing 7. In this later work it was suggested 97> that two different paths lead to 7 and 8. The benzyl ylid is the precursor to the Stevens product 8 as suggested earlier. However, an ion pair intermediate is the precursor to 7. 

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

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