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
Names
IUPAC name
Methyl trifluoromethanesulfonate
Other names
Trifluoromethanesulfonic acid, methyl ester
Triflic acid, methyl ester, methyl triflate
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.005.793
UNII
Properties
C2H3F3O3S
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)
Hydrolyzes
Hazards
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R-phrases (outdated) R10-R34
S-phrases (outdated) S26-S36/37/39-S45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

Synthesis

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

CF3SO2OH + (CH3O)2SO2 → CF3SO2OCH3 + CH3OSO2OH

Reactivity

The compound hydrolyzes violently upon contact with water:

CF3SO2OCH3 + H2O → CF3SO2OH + CH3OH

Methylation

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 polymerization

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

Polymerization of ε-caprolactone initiated by methyl triflate

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 also

References
  1. 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. 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.
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