Trifluoromethyltrimethylsilane

The reagent is prepared from trimethylsilyl chloride and bromotrifluoromethane in the presence of a phosphorus(III) reagent that serves as a halogen acceptor.[4]

In the presence of an anionic initiator (M⁺ X⁻), the reagent reacts with aldehydes and ketones to give a trimethylsilyl ether, the net product of insertion of the carbonyl into the Si-CF₃ bond. Hydrolysis gives trifluoromethyl methanols. The reagent also converts esters to trifluoromethyl ketones. A typical initiator is a soluble fluoride-containing species such as tetrabutylammonium fluoride, however simple alkoxides, e.g. KOtBu, are also effective.[5] The mechanism begins by generation of Si(CH₃)₃X and a highly reactive [CF₃]⁻ (trifluoromethide) intermediate. The [CF₃]⁻ attacks the carbonyl to generate an alkoxide anion. The alkoxide is silylated by the reagent to give the overall addition product, plus [CF₃]⁻, thus propagating an anionic chain reaction. The reagent competes with the carbonyl for the reactive intermediate, rapidly sequestering [CF₃]⁻ in a reversibly-generated -ate complex [(CF₃)₂Si(CH₃)₃]⁻. This -ate complex is unable to react directly with the carbonyl, resulting in powerful inhibition of the chain reaction by the reagent. This inhibitory process is common to all anion-initiated reactions of the reagent, with the identity of the counter-cation (M⁺) playing a major role in controlling the overall rate.[6]

The reagent has largely supplanted trifluoromethyllithium, which is not isolable and rapidly decomposes to yield lithium fluoride and difluorocarbene.