[56859-17-7] · C3H9KSi · Trimethylsilylpotassium · (MW 112.31)
Solubility: sol DME, THF, HMPA, hexane.
Analysis of Reagent Purity: 13C NMR (HMPA) d 4.2.6
Preparative Methods: prepared quantitatively by the cleavage of the silicon-silicon bond of Hexamethyldisilane with Potassium Hydride or potassium alkoxides (KOMe or Potassium t-Butoxide) (eqs 1 and 2).1,2,7-9 It can also be conveniently prepared by deprotonation of Me3SiH with KH (eq 3).2,3 These procedures circumvent the need to handle volatile organomercury compounds that previous routes required.10
Handling, Storage, and Precautions: solutions of Me3SiK are air and moisture sensitive and must be handled under inert atmospheres. The toxicity of Me3SiK is not currently known; however, the preparations employing Hexamethylphosphoric Triamide and 18-Crown-6 necessitate handling these solutions in a fume hood using chemically resistant gloves.
Me3SiK is a highly reactive nucleophile and one-electron transfer reagent. It readily couples with halides and enones via SN2 and 1,4-additions (eqs 4 and 5). When 1-bromohex-5-ene and benzophenone are treated with Me3SiK, electron transfer induced cyclization and dimerization occur (eqs 6 and 7). The course of these reactions can be substantially influenced by the nature of the solvent, resulting in enhancement of either nucleophilic substitution or electron transfer.1-3
Aryl halides can be converted in one step to aryl trimethylsilanes in good yields with Me3SiK (eq 8).11 These are particularly useful intermediates for directing electrophilic substitutions on carbon.12
Me3SiK stereospecifically deoxygenates substituted epoxides with inversion of stereochemistry. Reactions of cis- and trans-epoxides with Me3SiSiMe3 and KOMe give the trans- and cis-alkenes, respectively (eqs 9 and 10).4,5
Kevin J. Moriarty
Rhône-Poulenc Rorer, Collegeville, PA, USA