Methyl trifluoromethyl sulfonate

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Structural formula
Structural formula of methyl triflate
General
Surname Methyl trifluoromethyl sulfonate
other names
  • Trifluoromethanesulfonic acid methyl ester
  • Methyl trifluoromethanesulfonate
  • Methyl triflate
  • MeOTf
Molecular formula C 2 H 3 F 3 O 3 S
Brief description

clear colorless to light yellow liquid

External identifiers / databases
CAS number 333-27-7
EC number 206-371-7
ECHA InfoCard 100.005.793
PubChem 9526
Wikidata Q907614
properties
Molar mass 164.10 g mol −1
Physical state

liquid

density
Melting point

−64 ° C

boiling point
solubility

soluble in dichloromethane , sulfur dioxide , sulfolane , nitromethane , dimethyl sulfate

Refractive index

1.3240 - 1.3280 at 20 ° C

safety instructions
GHS labeling of hazardous substances
02 - Highly / extremely flammable 05 - Corrosive

danger

H and P phrases H: 226-314-318
P: 210-260-280-303 + 361 + 353-304 + 340-305 + 351 + 338-310
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . Refractive index: Na-D line , 20 ° C

Methyl trifluoromethylsulfonate (methyl triflate, MeOTf) is the methyl ester of the super acid trifluoromethanesulfonic acid and is used as a highly active methylating agent in preparative organic chemistry and as an initiator for cationic chain polymerization , especially for ring-opening polymerization of cyclic monomers.

Manufacturing

The synthesis of methyl trifluoromethyl sulfonate from the silver salt of trifluoromethanesulfonic acid and methyl iodide was first reported in 1956.

Production of methyl triflate from silver triflate

The yield of the reaction was only 69%.

Higher yields (70-80%) are achieved in the reaction of trifluoromethanesulphonic anhydride with methanol .

Methyl triflate from TFMSA anhydride

In this reaction, half of the expensive trifluoromethanesulfonic anhydride ( triflic anhydride ) used is lost.

When trifluoromethanesulfonic acid (HOTf) is reacted with dimethyl sulfate , MeOTf is formed in 81% yield, but together with the by-product sulfuric acid , which is contaminated with HOTf.

Methyl triflate from trifluoromethanesulfonic acid with dimethyl sulfate

The reaction of trifluoromethanesulfonic acid anhydride with dimethyl carbonate in the presence of catalytic amounts of HOTf gives an almost quantitative yield (98%) of methyl triflate .

Methyl triflate via TFMSA anhydride and dimethyl carbonate

Here, too, the disadvantage is the use of the expensive trifluoromethanesulfonic acid anhydride, which can be replaced by a combination of trifluoromethanesulfonic acid with an acid chloride - preferably benzoyl chloride .

Methyl triflate from trifluoromethylsulfonic acid, benzoyl chloride and DMC

This synthesis, based on easily accessible and inexpensive starting materials, delivers MeOTf in reproducible yield of 93% with high purity in addition to methyl benzoate as a usable by-product and appears to be the most economical route to methyl trifluoromethanesulfonate on an industrial scale.

properties

Methyl triflate is a clear, colorless, corrosive and flammable liquid which causes severe skin and mucous membrane damage if exposed or inhaled. MeOTf mixes with all organic solvents, but reacts with many e.g. T. very violently, such as B. water to trifluoromethanesulfonic acid. Because of the high activity of MeOTf as an alkylating agent, a significant carcinogenic and mutagenic potential must be assumed.

Applications

Methylation with methyl trifluoromethyl sulfonate

Methyl trifluoromethylsulphonate with the excellent leaving group trifluoromethanesulphonate is a very reactive methylating agent whose reactivity - measured by alcoholysis of model esters - is only due to Meerwein salts , such as. B. Trimethyloxoniumtetrafluoroborat is exceeded.

The gradation of the reactivity of methylating agents corresponds roughly to: (CH 3 ) 3 O + BF 4 - (trimethyloxonium tetrafluoroborate)> CF 3 SO 2 OCH 3 (methyl triflate)> FSO 2 OCH 3 ( methylfluorosulfonate ) >> H 3 C-phenyl -SO 2 OCH 3 ( methyl tosylate )> CH 3 SO 2 OCH 3 ( methyl methanesulfonate ) >> (CH 3 O) 2 SO 2 ( dimethyl sulfate )> CH 3 I ( methyl iodide )> CH 3 Br ( methyl bromide )

Compared to the solid and extremely hygroscopic Meerwein salt and the extremely toxic methyl fluorosulfonate and dimethyl sulfate, methyl triflate is easier to handle, less dangerous and requires less drastic reaction conditions, which lead to less or no racemization in the methylation of chiral molecules .

Methyl triflate has found wide application in organic chemistry for the introduction of methyl groups.

Thus, hydroxyl groups of carbohydrates are effectively and selectively methylated with MeOTf.

Aliphatic, alicyclic and aromatic nitrogen compounds and aliphatic phosphorus compounds are also converted into the corresponding quaternary ammonium or phosphonium salts in practically quantitative yield by reaction with methyl trifluoromethylsulfonate.

Preparation of 1,1-dimethylpyrrolidinium triflate

Some of these compounds are used as phase transfer catalysts or ionic liquids .

Also sterically hindered nitrogen aromatics, such as. B. 2,4,6-trimethylpyridine are methylated smoothly with methyl triflate, only extremely hindered pyridines such. B. 2,4,6-Tris ( t -butyl) pyridine hardly react.

Analogously, S compounds are methylated by methyl triflate to S-methylsulfonium salts.

S-methylation with methyl triflate

Cationic polymerization with methyl triflate

Methyl triflate initiates the living cationic polymerization of lactide and of lactones such as. B. β-propiolactone , ε-caprolactone or glycolide to the corresponding polylactones

Cationic polymerization of ε-caprolactone with methyl triflate

or of cyclic carbonates, such as. B. trimethylene carbonate and neopentylene carbonate (5,5-dimethyl-1,3-dioxan-2-one) to the corresponding polycarbonates.

2-alkyl-2-oxazolines, such as e.g. B. 2-Ethyl-2-oxazoline are polymerized by methyl trifluoromethylsulfonate also in a living cationic polymerization to poly (2-alkyloxazoline) n .

Individual evidence

  1. ↑ a b c d Entry on Methyl Trifluoromethanesulfonate at TCI Europe, accessed on July 22, 2016.
  2. ↑ a b c d e data sheet methyl trifluoromethanesulfonate from Sigma-Aldrich , accessed on July 22, 2016 ( PDF ).
  3. ↑ a b c d data sheet methyl trifluoromethanesulfonate from AlfaAesar, accessed on July 22, 2016 ( PDF )(JavaScript required) .
  4. ↑ a b c R.W. Alder, JGE Phillips, L. Huang, X. Huang: Methyltrifluoromethanesulfonate . In: e-EROS Encyclopedia of Reagents for Organic Synthesis . 2005, doi : 10.1002 / 047084289X.rm266m.pub2 .
  5. ↑ T. Gramstadt, RN Hazeldine: 33. Perfluoroalkyl derivatives of sulfur. Part IV. Perfluoroalkanesulphonic acids . In: J. Chem. Soc. 1956, p. 173-180 , doi : 10.1039 / JR9560000173 .
  6. ↑ T. Gramstadt, RN Hazeldine: 806. Perfluoroalkyl derivatives of sulfur. Part VII. Alkyl trifluoromethanesulphonates as alkylating agents, trifluoromethanesulphonic anhydride as a promoter for esterification, and some reactions of trifluoromethanesulphonic acid . In: J. Chem. Soc. 1957, p. 4069-4079 , doi : 10.1039 / JR9570004069 .
  7. ↑ BL Booth, RN Hazeldine, K. Laali: Alkyltrifluoromethanesulphonates as alkylating reagents for aromatic compounds . In: J. Chem. Soc. Perkin Trans. 1 . 1980, p. 2887-2893 , doi : 10.1039 / P19800002887 .
  8. ↑ CD Beard, K. Baum, V. Grakauskas: Synthesis of some novel trifluoromethanesulfonates and their reactions with alcohols . In: J. Org. Chem. Band 38 , no. 21 , 1973, p. 3673-3677 , doi : 10.1021 / jo00961a003 .
  9. ↑ a b Patent WO2002098844A1 : Method for producing perfluoroalkanesulfonic acid esters. Applied on May 4, 2002 , published on December 12, 2002 , Applicant: Merck Patent GmbH, Inventors: N. Ignatyev, M. Schmidt, U. Heider, P. Sartori, A. Kucheryna. ‌
  10. ↑ a b N.V. Ignat'ev, P. Barthen, A. Kucheryna, H. Willner, P. Sartori: A convenient synthesis of triflate anion ionic liquids and their properties . In: molecules . tape 17 , 2012, p. 5319-5338 , doi : 10.3390 / molecules17055319 .
  11. ↑ a b Patent WO2003053918A2 : Method for producing perfluoroalkanesulfonic acid esters and the salts thereof. Applied on November 25, 2002 , published on July 3, 2003 , Applicant: Merck Patent GmbH, Inventors: M. Schmidt, N. Ignatyev, U. Heider, P. Sartori, A. Kucheryna. ‌
  12. ^ Prudent Practices in the Laboratory: Handling and Management of Chemical Hazards, Washington, DC, 1995. National Academic Press, accessed July 28, 2016 .
  13. ↑ a b c P.J. Stang, M. Hanack, LR Subramanian: Perfluoroalkanesulfonic Esters: Methods of Preparation and Applications in Organic Chemistry . In: Synthesis . tape 1982 , no. 2 , 1982, p. 85-126 , doi : 10.1055 / s-1982-29711 .
  14. ↑ a b D.N. Kevill, GML Lin: A comparison of leaving-group abilities in reactions of powerful methylating agents . In: Tetrahedron Lett. tape 19 , no. 11 , 1978, p. 949-952 , doi : 10.1016 / S0040-4039 (01) 85422-8 .
  15. ^ ES Lewis, S. Vanderpool: Relative reactivities of phenoxides with methylating agents . In: J. Am. Chem. Soc. tape 99 , no. 6 , 1977, pp. 1946–1949 , doi : 10.1021 / ja00448a042 .
  16. ↑ MJ O'Donnell, WA Bruder, BW Daugherty, D. Liu, K. Wojciechowski: Nitrogen Alkylation of ship bases and amidines as a route to N-alkyl amino acids . In: Tetrahedron Lett. tape 25 , no. 34 , 1984, pp. 3651-3654 , doi : 10.1016 / 0040-4039 (84) 80096-9 .
  17. ↑ J. Arnarp, L. Kenne, B. Lindberg, J. Lönngren: Methylation of carbohydrates with methyl trifluoromethanesulfonate . In: Carbohyd. Res. Band 44 , no. 1 , 1975, p. C5-C7 , doi : 10.1016 / S0008-6215 (00) 84351-7 .
  18. ^ P. Prehm: Methylation of carbohydrates by methyl trifluoromethanesulfonate in trimethyl phosphate . In: Carbohyd. Res. Band 78 , no. 2 , 1980, p. 372-374 , doi : 10.1016 / 0008-6215 (80) 90018-X .
  19. ↑ V. Ulgar, O. López, I. Maya, JG Fernández-Bolanos, M. Bols: Synthesis of furan 4′-thio-C-nucleosides, their methylsulfonium and sulfoxide derivatives. Evaluation as glycosidase inhibitors . In: Tetrahedron . tape 59 , no. 16 , 2003, p. 2801-2809 , doi : 10.1016 / S0040-4020 (03) 00339-9 .
  20. ^ I. Rangel, M. Ricard, A. Ricard: Polymerization of L-lactide and ϵ-caprolactone in the presence of methyl trifluoromethanesulfonate . In: Macromol. Chem. Phys. tape 195 , no. 9 , 1994, pp. 3095-3101 , doi : 10.1002 / macp.1994.021950908 .
  21. ↑ JM Jonte, R. Dunsing, HR Kricheldorf: Polylactones. 4. Cationic Polymerization of Lactones by Means of Alkylsulfonates . In: J. Macromol. Sci: Part A Chemistry . tape 22 , no. 4 , 1985, pp. 495-514 , doi : 10.1080 / 00222338508056616 .
  22. ^ HR Kricheldorf, B. Weegen-Schulz, J. Jenssen: Cationic polymerization of aliphatic cyclocarbonates . In: Macromol. Symp. Band 132 , no. 1 , 1998, p. 421-430 , doi : 10.1002 / masy.19981320139 .
  23. ↑ M. Glassner, DR D'hooge, JY Park, PHM Van Steenberge, BD Monnery, M.-F. Reyniers, R. Hoogenboom: Systematic investigation of alkyl sulfonate initiators for the cationic ring-opening polymerization of 2-oxazolines revealing optimal combinations of monomers and initiators . In: Eur. Polym. J. Band 65 , 2015, p. 298–304 , doi : 10.1016 / j.eurpolymj.2015.01.019 .