Chloromethyl trimethylsilylmethyl sulfide

Chloromethyl trimethylsilylmethyl sulfide, (CH,)iSiCH,SCH2Cl (1). The sulfide is obtained in 69% yield by reaction of hydrogen chloride with a mixture of trime-thylsilymethanethiol and S-trioxane at 0°. 

Chloromethyl(trimethylsilylmethyl)sulfide, prepared from mercaptomethyltrimethyl-silane and paraformaldehyde, reacts with cesium fluoride to generate the thiocarbonyl ylide 73. Here again the reactive intermediate can be generated in the presence of an olefin leading to tetrahydrothiophenes (equation 132) or dimethyl acetylene dicarbox-ylate (DMAD) to produce the dihydrothiophene130 (equation 133). 

Annulation /raw-3,4-Disubstituted tetrahydrothiophenes are obtained from conjugated carbonyl compounds and chloromethyl trimethylsilylmethyl sulfide in a reaction mediated by CsF. When the conjugated carbonyl component bears a chiral auxiliary, the process is amenable to synthesis of enantiopure derivatives. 

Phthalazine (37) with chloromethyl trimethylsilylmethyl sulfide gave 2-[(tri-methylsilylmethylthio)methyl]phthalazinium chloride (38) (reactants, MeCN, 60°C, 1 h 96%) and thence l,10b-dihydro-3//-thiazolo[4,3-fl]phthalazine (39) (CsF, MeCN, 20°C, 48 h 92%) the reaction may be done as a one-pot procedure without isolation of the intermediate. 

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