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. The compound is closely related to methyl fluorosulfonate. Although there has yet to be a reported human fatality, while several cases were reported for methyl fluorosulfonate, methyl triflate is expected to have similar toxicity based on available evidence.

Synthesis

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

Reactivity

The compound hydrolyzes violently upon contact with water:

Methylation

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

Cationic polymerization

Methyl triflate initiates the living cationic polymerization of lactide and other lactones including β-propiolactone, ε-caprolactone and glycolide.
Cyclic carbonates like trimethylene carbonate and neopentylene carbonate can be polymerized to the corresponding polycarbonates. 2-alkyl-2-oxazolines, for example 2-ethyl-2-oxazoline, are also polymerized to polys.