Methyl trifluoromethanesulfonate, also commonly called methyl triflate and abbreviated MeOTf, is the

organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. Th ...

with the

formula In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a ''chemical formula''. The informal use of the term ''formula'' in science refers to the general construct of a relationship betwe ...

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 (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.

Synthesis

Methyl triflate is commercially available, however it may also be prepared in the laboratory by treating

dimethyl sulfate Dimethyl sulfate (DMS) is a chemical compound with formula (CH3O)2SO2. As the diester of methanol and sulfuric acid, its formula is often written as ( CH3)2 SO4 or Me2SO4, where CH3 or Me is methyl. Me2SO4 is mainly used as a methylating agent ...

with triflic acid. :CF₃SO₂OH + (CH₃O)₂SO₂ → CF₃SO₂OCH₃ + CH₃OSO₂OH

Reactivity

Hydrolysis

Upon contact with water, methyl triflate loses its methyl group, forming triflic acid and methanol: :CF₃SO₂OCH₃ + H₂O → CF₃SO₂OH + CH₃OH

Methylation

One ranking of methylating agents is (CH₃)₃O⁺ > CF₃SO₂OCH₃ ≈ FSO₂OCH₃ > (CH₃)₂SO₄ > CH₃I. Methyl triflate will alkylate many functional groups which are very poor nucleophiles such as

aldehyde In organic chemistry, an aldehyde () is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred to as an aldehyde but can also be classified as a formyl gro ...

amide In organic chemistry, an amide, also known as an organic amide or a carboxamide, is a compound with the general formula , where R, R', and R″ represent organic groups or hydrogen atoms. The amide group is called a peptide bond when it i ...

s, and

nitrile In organic chemistry, a nitrile is any organic compound that has a functional group. The prefix '' cyano-'' is used interchangeably with the term ''nitrile'' in industrial literature. Nitriles are found in many useful compounds, including me ...

s. 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. Kationische_Polymerisation_von_Caprolacton_mit_Methyltriflat

Kationische_Polymerisation_von_Caprolacton_mit_Methyltriflat

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

Applications

Radiochemistry

Carbon-11 methyl triflate ( 1CeOTf), or methyl triflate containing the carbon-11 isotope, is commonly used in

radiochemistry Radiochemistry is the chemistry of radioactive materials, where radioactive isotopes of elements are used to study the properties and chemical reactions of non-radioactive isotopes (often within radiochemistry the absence of radioactivity leads ...

to synthesize radioactively labeled compounds that can be traced in living organisms using

positron emission tomography Positron emission tomography (PET) is a functional imaging technique that uses radioactive substances known as radiotracers to visualize and measure changes in metabolic processes, and in other physiological activities including blood flow, ...

(PET). For example, 1CeOTf has been used extensively in the production of Pittsburgh Compound B, which first allowed β-amyloid plaques to be imaged in a living brain.

References

{{Reflist Methylating agents Methyl esters Triflate esters