Formal Hydrotrimethylsilylation of Styrenes with Anti-Markovnikov Selectivity Using Hexamethyldisilane

A combination of CsF and hexamethyldisilane in DMSO enabling an anti-Markovnikov formal hydrotrimethylsilylation of styrenes is reported. Mechanistic investigations detail the reaction pathways, including in situ generation of a silyl anion, the addition of this silyl anion onto the alkene to form a carbanion, and this carbanion is then protonated by DMSO. The choice of the solvent to match its reactivity with the carbanion and silyl anion is key to the success of this reaction.