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Methyl trifluoromethanesulfonate

Methyl trifluoromethanesulfonate
Structural formula of methyl triflate
Ball-and-stick model of methyl triflate
Names
Preferred 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 Edit this at Wikidata
EC Number
  • 206-371-7
UNII
UN number 2924
  • InChI=1S/C2H3F3O3S/c1-8-9(6,7)2(3,4)5/h1H3 checkY
    Key: OIRDBPQYVWXNSJ-UHFFFAOYSA-N checkY
  • InChI=1/C2H3F3O3S/c1-8-9(6,7)2(3,4)5/h1H3
    Key: OIRDBPQYVWXNSJ-UHFFFAOYAL
  • COS(=O)(=O)C(F)(F)F
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[1]
Occupational safety and health (OHS/OSH):
Main hazards
 Corrosive
GHS labelling:
Danger
H226, H301, H311, H314, H330
P210, P233, P303+P361+P353, P304+P340+P310, P305+P351+P338, P380
Flash point 38 °C (100 °F; 311 K)
Related compounds
Related compounds
 Methyl fluorosulfonate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkY☒N ?)

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.[2] The compound is closely related to methyl fluorosulfonate (FSO2OCH3). Although there has yet to be a reported human fatality, several cases were reported for methyl fluorosulfonate (LC50 (rat, 1 h) = 5 ppm), and methyl triflate is expected to have similar toxicity based on available evidence.[3][verification needed]

Synthesis

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Methyl triflate is commercially available, however it may also be prepared in the laboratory by treating dimethyl sulfate with triflic acid.[4]

CF3SO2OH + (CH3O)2SO2 → CF3SO2OCH3 + CH3OSO2OH

Reactivity

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Hydrolysis

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Upon contact with water, methyl triflate loses its methyl group, forming triflic acid and methanol:

CF3SO2OCH3 + H2O → CF3SO2OH + CH3OH

Methylation

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One ranking of methylating agents is (CH3)3O+ > CF3SO2OCH3 ≈ FSO2OCH3 > (CH3)2SO4 > CH3I.[4] 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.[2] Its ability to methylate N-heterocycles is exploited in certain deprotection schemes.[5]

Cationic polymerization

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Methyl triflate initiates the living cationic polymerization of lactide[6] and other lactones including β-propiolactone, ε-caprolactone and glycolide.[7]

Polymerization of ε-caprolactone initiated by methyl triflate
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.[8] 2-alkyl-2-oxazolines, for example 2-ethyl-2-oxazoline, are also polymerized to poly(2-alkyloxazoline)s.[9]

Applications

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Radiochemistry

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Carbon-11 methyl triflate ([11C]MeOTf[10]), or methyl triflate containing the carbon-11 isotope, is commonly used in radiochemistry to synthesize radioactively labeled compounds that can be traced in living organisms using positron emission tomography (PET). For example, [11C]MeOTf has been used extensively in the production of Pittsburgh Compound B, which first allowed β-amyloid plaques to be imaged in a living brain.

See also

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References

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  1. ^ "Methyl trifluoromethanesulfonate". Sigma-Aldrich. Retrieved 31 October 2021.
  2. ^ a b Alder, Roger W.; Phillips, Justin G. E.; Huang Lijun; Huang Xuefei (2005). "Methyltrifluoromethanesulfonate". Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.rm266m.pub2. ISBN 0471936235.
  3. ^ Alder, R. W.; Sinnott, M. L.; Whiting, M. C.; Evans, D. A. (1978). "Hazards of powerful methylating agents". Chemistry in Britain. Vol. 14, no. 7. p. 324. Miscited as ——— (1976) Chem. Eng. News, vol. 54, no. 36, p. 56 in Alder et al. 2005
  4. ^ 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.
  5. ^ Albert I. Meyers & Mark E. Flanagan (1998). "2,2′-Dimethoxy-6-formylbiphenyl". Organic Syntheses; Collected Volumes, vol. 9, p. 258.
  6. ^ 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.
  7. ^ 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.
  8. ^ 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.
  9. ^ 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.
  10. ^ Jewett, D. M. (1992). "A simple synthesis of [11C]methyl triflate". International Journal of Radiation Applications and Instrumentation, Part A. 43 (11): 1383–1385. doi:10.1016/0883-2889(92)90012-4. hdl:2027.42/29777. ISSN 0883-2889. PMID 1333459.