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. The ...
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 betwee ...
CF
3SO
2OCH
3. It is a colourless liquid which finds use in organic chemistry as a powerful
methylating agent.
The compound is closely related to
methyl fluorosulfonate
Methyl fluorosulfonate, also known as magic methyl, is the organic compound with the formula FSO2OCH3. It is a colorless liquid that is used as a strong methylating agent in organic synthesis. Because of its extreme toxicity, it has largely been ...
(FSO
2OCH
3). Although there has yet to be a reported human fatality, several cases were reported for methyl fluorosulfonate (LC
50 (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 with triflic acid.
:CF
3SO
2OH + (CH
3O)
2SO
2 → CF
3SO
2OCH
3 + CH
3OSO
2OH
Reactivity
Hydrolysis
Upon contact with water, methyl triflate loses its methyl group, forming triflic acid and methanol:
:CF
3SO
2OCH
3 + H
2O → CF
3SO
2OH + CH
3OH
Methylation
One ranking of methylating agents is
(CH3)3O+ > CF
3SO
2OCH
3 ≈ FSO
2OCH
3 >
(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 grou ...
s, 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 is ...
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 met ...
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
A protecting group or protective group is introduced into a molecule by chemical modification of a functional group to obtain chemoselectivity in a subsequent chemical reaction. It plays an important role in multistep organic synthesis.
In man ...
schemes.
Cationic polymerization
Methyl triflate initiates the living cationic polymerization Living cationic polymerization is a living polymerization technique involving cationic propagating species. It enables the synthesis of very well defined polymers (low molar mass distribution) and of polymers with unusual architecture such as star ...
of lactide
Lactide is the lactone cyclic ester derived by multiple esterification between two (usually) or more molecules from lactic acid (2-hydroxypropionic acid) or other hydroxy carboxylic acid. They are designated as dilactides, trilactides, etc., acco ...
and other lactones including β-propiolactone, ε-caprolactone and glycolide
Polyglycolide or poly(glycolic acid) (PGA), also spelled as polyglycolic acid, is a biodegradable, thermoplastic polymer and the simplest linear, aliphatic polyester. It can be prepared starting from glycolic acid by means of polycondensation or r ...
.
Cyclic carbonates like trimethylene carbonate
Trimethylene carbonate, or 1,3-propylene carbonate, is a 6-membered cyclic carbonate ester. It is a colourless solid that upon heating or catalytic ring-opening converts to poly(trimethylene carbonate) (PTMC). Such polymers are called aliphatic p ...
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 t ...
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 Metabolism, metabolic processes, and in other physiological activities including bl ...
(PET). For example, 1CeOTf has been used extensively in the production of Pittsburgh Compound B
Pittsburgh compound B (PiB) is a radioactive analog of thioflavin T, which can be used in positron emission tomography scans to image beta-amyloid plaques in neuronal tissue. Due to this property, Pittsburgh compound B may be used in investiga ...
, which first allowed β-amyloid plaques to be imaged in a living brain.
See also
* Triflate
In organic chemistry, triflate (systematic name: trifluoromethanesulfonate), is a functional group with the formula and structure . The triflate group is often represented by , as opposed to −Tf, which is the triflyl group, . For example, ' ...
* Magic methyl
Methyl fluorosulfonate, also known as magic methyl, is the organic compound with the formula FSO2OCH3. It is a colorless liquid that is used as a strong methylating agent in organic synthesis. Because of its extreme toxicity, it has largely been ...
References
{{Reflist
Methylating agents
Methyl esters
Triflate esters