Methyl trifluoromethanesulfonate

Methyl trifluoromethanesulfonate, also commonly called methyl triflate and abbreviated MeOTf, is the organic compound with the formula CF3SO2OCH3. It is a colourless liquid which finds use in organic chemistry as a powerful methylating agent.[1] The compound is closely related to methyl fluorosulfonate (FSO2OCH3). Although there has yet to be a reported human fatality, while several cases were reported for methyl fluorosulfonate (LC50 (rat, 1 h) = 5 ppm), methyl triflate is expected to have similar toxicity based on available evidence.[1]

Methyl trifluoromethanesulfonate
Structural formula of methyl triflate
Ball-and-stick model of methyl triflate
Preferred IUPAC name
Methyl trifluoromethanesulfonate
Other names
Trifluoromethanesulfonic acid, methyl ester
Triflic acid, methyl ester, methyl triflate
3D model (JSmol)
ECHA InfoCard 100.005.793 Edit this at Wikidata
  • InChI=1S/C2H3F3O3S/c1-8-9(6,7)2(3,4)5/h1H3 checkY
  • InChI=1/C2H3F3O3S/c1-8-9(6,7)2(3,4)5/h1H3
  • COS(=O)(=O)C(F)(F)F
Molar mass 164.10 g·mol−1
Appearance Colourless Liquid
Density 1.496 g/mL
Melting point −64 °C (−83 °F; 209 K)
Boiling point 100 °C (212 °F; 373 K)
Main hazards Corrosive
R-phrases (outdated) R10-R34
S-phrases (outdated) S26-S36/37/39-S45
Flash point 38 °C (100 °F; 311 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references


Methyl triflate is commercially available, however it may also be prepared in the laboratory by treating dimethyl sulfate with triflic acid.[2]



The compound hydrolyzes violently upon contact with water:



One ranking of methylating agents is (CH3)3O+ > CF3SO2OCH3 ≈ FSO2OCH3 > (CH3)2SO4 > CH3I.[2] Methyl triflate will alkylate many functional groups which are very poor nucleophiles such as aldehydes, amides, and nitriles. It does not methylate benzene or the bulky 2,6-di-tert-butylpyridine.[1] Its ability to methylate N-heterocycles is exploited in certain deprotection schemes.[3]

Cationic polymerizationEdit

Methyl triflate initiates the living cationic polymerization of lactide[4] and other lactones including β-propiolactone, ε-caprolactone and glycolide.[5]

Cyclic carbonates like trimethylene carbonate and neopentylene carbonate (5,5-dimethyl-1,3-dioxan-2-one) can be polymerized to the corresponding polycarbonates.[6] 2-alkyl-2-oxazolines, for example 2-ethyl-2-oxazoline, are also polymerized to poly(2-alkyloxazoline)s.[7]

See alsoEdit


  1. ^ a b c Roger W. Alder; Justin G. E. Phillips; Lijun Huang; Xuefei Huang (2005). "Methyltrifluoromethanesulfonate". Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.rm266m.pub2. ISBN 0471936235.
  2. ^ a b Stang, Peter J.; Hanack, Michael; Subramanian, L. R. (1982). "Perfluoroalkanesulfonic Esters: Methods of Preparation and Applications in Organic Chemistry". Synthesis. 1982 (2): 85–126. doi:10.1055/s-1982-29711. ISSN 0039-7881.
  3. ^ Albert I. Meyers & Mark E. Flanagan (1998). "2,2′-Dimethoxy-6-formylbiphenyl". Organic Syntheses.; Collective Volume, 9, p. 258
  4. ^ Rangel, Irma; Ricard, Michèle; Ricard, Alain (1994). "Polymerization of L-lactide and ε-caprolactone in the presence of methyl trifluoromethanesulfonate". Macromolecular Chemistry and Physics. 195 (9): 3095–3101. doi:10.1002/macp.1994.021950908.
  5. ^ Jonté, J. Michael; Dunsing, Ruth; Kricheldorf, Hans R. (1985). "Polylactones. 4. Cationic Polymerization of Lactones by Means of Alkylsulfonates". Journal of Macromolecular Science: Part A - Chemistry. 22 (4): 495–514. doi:10.1080/00222338508056616. ISSN 0022-233X.
  6. ^ Kricheldorf, Hans R.; Weegen-Schulz, Bettina; Jenssen, Jörg (1998). "Cationic polymerization of aliphatic cyclocarbonates". Macromolecular Symposia. 132 (1): 421–430. doi:10.1002/masy.19981320139.
  7. ^ Glassner, Mathias; D’hooge, Dagmar R.; Young Park, Jin; Van Steenberge, Paul H.M.; Monnery, Bryn D.; Reyniers, Marie-Françoise; Hoogenboom, Richard (2015). "Systematic investigation of alkyl sulfonate initiators for the cationic ring-opening polymerization of 2-oxazolines revealing optimal combinations of monomers and initiators". European Polymer Journal. 65: 298–304. doi:10.1016/j.eurpolymj.2015.01.019. hdl:1854/LU-5924229.