Phenyldimethylsilyllithium

The phenyldimethylsilyl group is commonly used in organic synthesis, partly because it forms a lithium reagent more easily than trialkylsilyl groups. It is easily introduced into a molecule, either from a direct reaction with phenyldimethylsilyllithium (PhMe₂SiLi, 1), or from the addition of the silylcuprate 2 (or zincate) to α,β-unsaturated carbonyl compounds (1,4-addition), to acid chlorides (to give acylsilanes), or to acetylenes (to give vinylsilanes). After the phenyl dimethylsilyl group has performed its task in the synthesis it can be easily removed, either as an electrofugal group in an elimination or, and most notably, via the silyl-to-hydroxyl conversion, which proceeds with retention of stereochemical configuration.

Phenyldimethylsilyllithium has been shown to react directly with iminium salts, esters, amides and aldehydes/ketones, to give α-silyl amines, disilyl alcohols, acylsilanes and α-silyl alcohols. α-Silyl alcohols can be converted, by way of the α-silyl iodides, to the α-metallated silanes which react with aldehydes or acid chlorides to set up, stereospecifically, the components of the Peterson elimination. In addition, esters, ketones and epoxides can be converted to alkenes by the use of PhMe₂SiLi, and α-siloxy ketones can be converted to ketones, the mechanism of which involves a Brook rearrangement to reveal a regiodefined silyl enol ether.