Trimethylsilyl trifluoromethanesulfonate
{{Chembox
| ImageFile = TmsOTf.svg
| ImageSize = 200px
| ImageAlt =
| PIN = Trimethylsilyl trifluoromethanesulfonate
| OtherNames = TMSOTf
Trimethylsilyl triflate
TMS triflate
Trifluoromethanesulfonic acid trimethylsilyl ester
|Section1={{Chembox Identifiers
| CASNo = 27607-77-8
| CASNo_Ref = {{cascite|correct|CAS}}
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = Z84V0CBH9J
| PubChem = 65367
| SMILES = C[Si](C)(C)OS(=O)(=O)C(F)(F)F
}}
|Section2={{Chembox Properties
| C=4 | H=9 | F=3 | O=3 | S=1 | Si=1
| Appearance = Colorless liquid
| Density = 1.225 g/mL
| MeltingPtC =
| BoilingPtC = 140
| Solubility =
}}
|Section3={{Chembox Hazards
| MainHazards =
| FlashPt =
| AutoignitionPt =
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}}
Trimethylsilyl trifluoromethanesulfonate (TMSOTf) is an organosilicon compound with the formula {{chem2|(CH3)3SiO3SCF3}}. It is a colorless moisture-sensitive liquid. It is the trifluoromethanesulfonate derivative of trimethylsilyl.{{cite journal|title=Trimethylsilyl Trifluoromethanesulfonate|author=Joseph Sweeney |author2=Gemma Perkins |author3=Enrique Aguilar |author4=Manuel A. Fernández-Rodríguez |author5=Rodolfo Marquez |author6=Eric Amigues |author7=Ricardo Lopez-Gonzalez |journal=Encyclopedia of Reagents for Organic Synthesis|year=2018|doi=10.1002/047084289X.rt338|isbn=978-0-471-93623-7 }} It is mainly used to activate ketones and aldehydes in organic synthesis.
Reactions
TMSOTf is quite sensitive toward hydrolysis:
:{{chem2|(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:{{cite journal |doi=10.15227/orgsyn.092.0309 |title=(S)-1,1-Diphenylprolinol Trimethylsilyl Ether |date=2015 |last1=Boeckman |first1=Robert |first2=Douglas J.|last2=Tusch|first3=Kyle F.|last3=Biegasiewicz|journal=Organic Syntheses |volume=92 |pages=309–319 |doi-access=free }}
:{{chem2|(CH3)3SiO3SCF3 + ROH + Et3N -> ROSi(CH3)3Si + [Et3NH]O3SCF3}}
A common use of {{chem2|(CH3)3SiO3SCF3}} is for the preparation of silyl enol ethers.{{cite journal|doi=10.15227/orgsyn.069.0129|title=N-Fluoropyridinium Triflate: An Electrophilic Fluorinating Agent|journal=Organic Syntheses|volume=69|page=129|year=1990|first1=Teruo|last1=Umemoto|first2=Kyoichi |last2=Tomita|first3=Kosuke|last3=Kawada}}Efficient Stereoselective Synthesis of Proanthocyanidin Trimers with TMSOTf-Catalyzed Intermolecular Condensation. Akiko Saito, Akira Tanaka, Makoto Ubukata and Noriyuki Nakajima, Synlett, 2004, volume 6, pages 1069-1073, {{doi|10.1055/s-2004-822905}} One example involves the synthesis of the silyl enol ether of camphor:
:File:Tms enol ether formation.svg{{clear-left}}
It was also used in Takahashi Taxol total synthesis and in chemical glycosylation reactions.{{cite journal|doi=10.15227/orgsyn.081.0225|title=Synthesis and Use of Glycosyl Phosphates as Glycosyl Donors|journal=Organic Syntheses|volume=81|page=225|year=2005|first1=Kerry R. |last1=Love|first2=Peter H. |last2=Seeberger|doi-access=free}}
Trimethylsilyl trifluoromethanesulfonate has a variety of other specialized uses. It has been used to install tert-alkyl groups on phosphine (R = alkyl):{{Cite journal|last1=Barber|first1=Thomas|last2=Argent|first2=Stephen P.|last3=Ball|first3=Liam T.|date=2020-05-15|title=Expanding Ligand Space: Preparation, Characterization, and Synthetic Applications of Air-Stable, Odorless Di- tert -alkylphosphine Surrogates|url=https://pubs.acs.org/doi/10.1021/acscatal.0c01414|journal=ACS Catalysis|language=en|volume=10|issue=10|pages=5454–5461|doi=10.1021/acscatal.0c01414|s2cid=219017552|issn=2155-5435}}
:PH3 + R3C–OAc + Me3SiOTf → [(R3C)2PH2]OTf
Deprotection of Boc-protected amines can be achieved using trimethylsilyl trifluoromethanesulfonate and triethylamine or 2,6-lutidine.{{cite journal |last1=Kuehne |first1=Martin E. |last2=Xu |first2=Feng |title=Syntheses of Strychnan- and Aspidospermatan-Type Alkaloids. 10. An Enantioselective Synthesis of (−)-Strychnine through the Wieland−Gumlich Aldehyde |journal=The Journal of Organic Chemistry |date=1 December 1998 |volume=63 |issue=25 |pages=9427–9433 |doi=10.1021/jo9813989}}{{cite journal |last1=Doi |first1=Takayuki |last2=Numajiri |first2=Yoshitaka |last3=Munakata |first3=Asami |last4=Takahashi |first4=Takashi |title=Total Synthesis of Apratoxin A |journal=Organic Letters |date=1 February 2006 |volume=8 |issue=3 |pages=531–534 |doi=10.1021/ol052907d|pmid=16435877 }}
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.