Trifluoromethyltrimethylsilane (known as Ruppert-Prakash reagent, TMSCF₃) is an organosilicon compound with the formula CF₃Si(CH₃)₃. It is a colorless liquid. The compound is a

reagent In chemistry, a reagent ( ) or analytical reagent is a substance or compound added to a system to cause a chemical reaction, or test if one occurs. The terms ''reactant'' and ''reagent'' are often used interchangeably, but reactant specifies a ...

used in organic chemistry for the introduction of the

trifluoromethyl The trifluoromethyl group is a functional group that has the formula . The naming of is group is derived from the methyl group (which has the formula ), by replacing each hydrogen atom by a fluorine atom. Some common examples are trifluoromethane ...

group A group is a number of persons or things that are located, gathered, or classed together. Groups of people * Cultural group, a group whose members share the same cultural identity * Ethnic group, a group whose members share the same ethnic iden ...

. The compound was first prepared in 1984 by Ingo Ruppert and further developed as a reagent by G. K. Surya Prakash.

Preparation

The reagent is prepared from trimethylsilyl chloride and

bromotrifluoromethane Bromotrifluoromethane, commonly referred to by the code numbers Halon 1301, R13B1, Halon 13B1 or BTM, is an organic halide with the chemical formula carbon, Cbromine, Brfluorine, F3. It is used for gaseous fire suppression as a far less toxic alte ...

in the presence of a phosphorus(III) reagent that serves as a halogen acceptor.

Use in organic synthesis

In the presence of a metal salt (M⁺ X⁻), the reagent reacts with

aldehydes In organic chemistry, an aldehyde () (lat. ''al''cohol ''dehyd''rogenatum, dehydrogenated alcohol) is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred ...

and

ketones In organic chemistry, a ketone is an organic compound with the structure , where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group (a carbon-oxygen double bond C=O). The simplest ketone is acetone ( ...

to give a trimethylsilyl ether, the net product of insertion of the carbonyl into the Si-CF₃ bond.

Hydrolysis Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution reaction, substitution, elimination reaction, elimination, and solvation reactions in which water ...

gives trifluoromethyl

methanol Methanol (also called methyl alcohol and wood spirit, amongst other names) is an organic chemical compound and the simplest aliphatic Alcohol (chemistry), alcohol, with the chemical formula (a methyl group linked to a hydroxyl group, often ab ...

s. The reagent also converts esters to trifluoromethyl

. A typical initiator is a soluble fluoride-containing species such as tetrabutylammonium fluoride; however, simple alkoxides such as KOtBu are also effective. The mechanism begins by generation of Si(CH₃)₃X and a highly reactive F₃sup>− (trifluoromethide) intermediate. The F₃sup>− attacks the carbonyl to generate an alkoxide anion. The alkoxide is silylated by the reagent to give the overall addition product, plus F₃sup>−, thus propagating an anionic chain reaction. The reagent competes with the carbonyl for the reactive intermediate, rapidly sequestering F₃sup>− in a reversibly-generated -ate complex CF₃)₂Si(CH₃)₃sup>−. 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.{{cite journal, title=Anion-Initiated Trifluoromethylation by TMSCF₃: Deconvolution of the Siliconate–Carbanion Dichotomy by Stopped-Flow NMR/IR, author1=Craig P. Johnston, author2=Thomas H. West, author3=Ruth E. Dooley, author4=Marc Reid, author5= Ariana B. Jones, author6= Edward J. King, author7=Andrew G. Leach, author8=Guy C. Lloyd-Jones , journal=Journal of the American Chemical Society, volume=140, issue=35, pages=11112–11124, year=2018, doi=10.1021/jacs.8b06777, pmid=30080973, pmc=6133236, bibcode=2018JAChS.14011112J , hdl=10023/16552 The reagent has largely supplanted trifluoromethyllithium, which is not isolable and rapidly decomposes to yield

lithium fluoride Lithium fluoride is an inorganic compound with the chemical formula LiF. It is a colorless solid that transitions to white with decreasing crystal size. Its structure is analogous to that of sodium chloride, but it is much less soluble in water. ...

and

difluorocarbene Difluorocarbene is the chemical compound with formula CF2. It has a short half-life, 0.5 and 20 ms, in solution and in the gas phase, respectively.Douglas A Jean Osteraas "Difluorocarbene Modification of Polymer and Fiber Surfaces," ''Journal ...

References

Trifluoromethyl compounds Reagents for organic chemistry Carbosilanes Trimethylsilyl compounds