Trifluoromethyltrimethylsilane

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 used in organic chemistry for the introduction of the trifluoromethyl group. The compound was first prepared in 1984 by Ingo Ruppert^[1] and further developed as a reagent by G. K. Surya Prakash.^[2][3]

Trifluoromethyltrimethylsilane

Names
Preferred IUPAC name Trimethyl(trifluoromethyl)silane
Other names Ruppert's reagent; TFMTMS; CF3SiMe3
Identifiers
CAS Number	81290-20-2 Y
3D model (JSmol)	Interactive image
ChemSpider	480635
ECHA InfoCard	100.106.346
PubChem CID	552549
UNII	A009786QPJ Y
CompTox Dashboard (EPA)	DTXSID601336260 DTXSID20338998, DTXSID601336260
InChI InChI=1S/C4H9F3Si/c1-8(2,3)4(5,6)7/h1-3H3 Key: MWKJTNBSKNUMFN-UHFFFAOYSA-N
SMILES C[Si](C)(C)C(F)(F)F
Properties
Chemical formula	C4H9F3Si
Molar mass	142.196 g·mol−1
Appearance	Colorless liquid
Density	0.9626 g/cm3 at 20 °C
Boiling point	54 to 55 °C (129 to 131 °F; 327 to 328 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) Infobox references

Preparation

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

Use in organic synthesis

In the presence of a metal salt (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 such as 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.