Iodomethyl trimethylsilane

Treatment of a-sulfonyl carbanion with (iodomethyl)trimethylsilane gave / -trimethylsilyl sulfones289-291. Alkylation of / -trimethylsilyl sulfones 235 gave various /Mrimethylsilyl sulfones292. The use of (iodomethyl)tributylstannane instead of (iodomethyl)trimethylsilane was shown to afford a tributylstannanyl derivative293. This compound has been used for syntheses of terminal olefins289-293. 

A major detraction to the p-silyl sulfone route to alkenes is its narrow scope, owing to the paucity of methods for preparing the requisite p-silyl sulfones. The method has so far been largely restricted to monosubstituted and 1,1-disubstituted ethylene derivatives because the P-silyl sulfones have usually been most conveniently and economically prepared by the alkylation of a sulfone anion with iodomethyl-trimethylsilane. Unfortunately higher haloalkylsilanes are difficult to prepare and their alkylation chemistry remains unexplored. 

The best results are obtained with the use of alkali metal hydrides (NaH, KH) in THF, DME, or DMF. The reaction works well in THF or DME with activated halides such as ethyl bromoac-etate, ten-butyl bromoacetate, - ethyl 2-bromobutyratc, ethyl T-broniobulyrale.- (iodom-ethyl)trimethylstannane, " (iodomethyl)trimethylsilane, benzoyl bromide,- benzyl bro-mide, - farnesyl bromide,- " alkyl 4-bromocrotonates, l-(bromomethyl)naphtalene,- andN-bromomethylphthalimide but gives poor results with primary alkyl halides.- Primary and secondary alkyl halides, bromides and iodides (Scheme 8.16), react satisfactorily in dMF or DMSO, although bulky electrophiles give poor results. In DMSO the expected product is frequently contaminated by the dialkylation product. ... 

Alternative Routes to Substituted (2-Phenylsulfonylethyl)-trimethylsilanes. Although the fluoride-induced elimination is a reliable and efficient method for synthesizing alkenes, the requisite silyl sulfone precursors are often better prepared by methods which avoid the use of (2). For example, eq 3 illustrates an alternative synthesis of 2,2-dialkyl-2-(phenylsulfonylethyl)trimethyl-silanes involving alkylation of a lithio sulfone with (iodomethyl)-trimethylsilane. ... 

Preparation. Compound 2 is easily obtained via a two-step sequence starting from the reaction of commercially available methanesulfonyl chloride and ammonium chloride in the presence of sodium hydroxide (eq 1). The product bis(methane-sulfonimide) (1) is then treated with 3 equivof LiHMDS at —78 °C to give a trianion. Subsequent alkylation with 2 equiv of commercially available (iodomethyl)trimethylsilane and warming to room tert5)erature affords the desired sulfonitnide 2 in good yield (eq 1). 

This compound is efficiently synthesized via N-alkylation reaction of the saccharin sodium salt with (iodomethyl)trimethylsilane (Scheme 24.7) (64). 

Scheme 24.7 N-Alkylation of the Saccharin Sodium Salt By (iodomethyl) trimethylsilane.

---