Trimethylsilyl trifluoromethanesulfonate

Trimethylsilyl trifluoromethanesulfonate (TMSOTf) is an organosilicon compound with the formula (CH₃)₃SiO₃SCF₃. It is a colorless moisture-sensitive liquid. It is the trifluoromethanesulfonate derivative of trimethylsilyl.^[1] It is mainly used to activate ketones and aldehydes in organic synthesis.

Trimethylsilyl trifluoromethanesulfonate

Names
Preferred IUPAC name Trimethylsilyl trifluoromethanesulfonate
Other names TMSOTf Trimethylsilyl triflate TMS triflate Trifluoromethanesulfonic acid trimethylsilyl ester
Identifiers
CAS Number	27607-77-8 Y
3D model (JSmol)	Interactive image
ChemSpider	58839
ECHA InfoCard	100.044.136
EC Number	248-565-4
PubChem CID	65367
UNII	Z84V0CBH9J Y
CompTox Dashboard (EPA)	DTXSID2067325
InChI InChI=1S/C4H9F3O3SSi/c1-12(2,3)10-11(8,9)4(5,6)7/h1-3H3 Key: FTVLMFQEYACZNP-UHFFFAOYSA-N
SMILES C[Si](C)(C)OS(=O)(=O)C(F)(F)F
Properties
Chemical formula	C4H9F3O3SSi
Molar mass	222.25 g·mol−1
Appearance	Colorless liquid
Density	1.225 g/mL
Boiling point	140 °C (284 °F; 413 K)
Hazards
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H226, H314
Precautionary statements	P210, P233, P240, P241, P242, P243, P260, P264, P280, P301+P330+P331, P302+P361+P354, P303+P361+P353, P304+P340, P305+P354+P338, P316, P321, P363, P370+P378, P403+P235, P405, P501
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Reactions

TMSOTf is quite sensitive toward hydrolysis:

(CH₃)₃SiO₃SCF₃ + H₂O → (CH₃)₃SiOH + HO₃SCF₃

It is far more electrophilic than trimethylsilyl chloride.

Related to its tendency to hydrolyze, TMSOTf is effective for silylation of alcohols:^[2]

(CH₃)₃SiO₃SCF₃ + ROH + Et₃N → ROSi(CH₃)₃Si + [Et₃NH]O₃SCF₃

A common use of (CH₃)₃SiO₃SCF₃ is for the preparation of silyl enol ethers.^[3][4] One example involves the synthesis of the silyl enol ether of camphor:

It was also used in Takahashi Taxol total synthesis and in chemical glycosylation reactions.^[5]

Trimethylsilyl trifluoromethanesulfonate has a variety of other specialized uses. It has been used to install tert-alkyl groups on phosphine (R = alkyl):^[6]

PH₃ + R₃C–OAc + Me₃SiOTf → [(R₃C)₂PH₂]OTf

Deprotection of Boc-protected amines can be achieved using trimethylsilyl trifluoromethanesulfonate and triethylamine or 2,6-lutidine.^[7][8]

TMSOTf is also a useful reagent to replace metal-halogen bonds with a covalent M-O(SO2CF3) bond, the by-product being the highly volatile TMSCl which is easily removed.