2-methyl-3- - -trifluoromethanesulfonate

Yoshiyasu Terao Minoru Sekiya University of Shizuoka, Japan 

Alternate Name R = CF3, methyl triflate R = F, Magic Methyl. 

Solubility both reagents are miscible with all organic solvents, but react with many. They are only si sol water, but hydrolyze rapidly as they dissolve. Useful inert solvents are CH2CI2, SO2, sulfolane, nitromethane, Me2S04, and Me3P04. 

Form Supplied in methyl triflate (MeOTf) is available as a colorless liquid. Methyl fluorosulfonate (Me0S02p) was formerly available as Magic MethyF but has been withdrawn (see below). 

Preparative Methods both reagents are prepared by distilling an equimolar mixture of the corresponding acid with Dimethyl Sulfate in an all-glass apparatus with a short Vigreux column. They may be dried by standing over fused K2CO3 and redistillation. Trifluoromethanesulfonic Acid and Fluorosulfuric Acid are both available, and are comparably priced. 

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Higher perfluoroalkanesulfonates are slightly more reactive than triflates toward nucleophilic displacements. The rate constants for acetolysis of methyl nonafluorobutanesulfonate [6401 -03-2J, methyl trifluoromethanesulfonate [333-27-7] and methyl toluenesulfonate [80-48-8] are 1.49 x, ... 

To a solution of dihydronaphthalene 41 (250 mg, 0.77 mmol) in CH2CI2 (5 mL) was added methyl trifluoromethanesulfonate (227 mg, 1.38 mmol). The mixture was stirred at rt until the starting material had been completely consumed as judged by TLC analysis (3 h). The mixture was cooled to 0°C and a solution of NaBHt (111 mg, 2.92 mmol) in 4 1 MeOH THF (3 mL) was slowly added. The mixture was warmed to rt then quenched with saturated aqueous ammonium chloride (50 mL). The resulting mixture was extracted with CH2CI2 (3 X 50 mL) and the combined organic extracts were dried over anhydrous sodium sulfate, filtered, and concentrated in vacuo. The resulting material was dissolved in 4 1 THF/H2O (5 mL) and oxalic acid (485 mg, 3.85 mmol) was added. The reaction... 

Quaternization is difficult benzofuroxan is unaffected by triethyl-oxonium fluoroborate. With methyl trifluoromethanesulfonate, an interesting rearrangement occurs, and l-hydroxybenzimidazole-3-oxide (39, R = H) is formed, probably via the N-quaternized derivative (38). Compound 39 (R = Ceils) has been prepared similarly. 

Dibenz[r,e,]azcpinium salts, e.g. 3 and 6, arc also obtained by O- and 5-alkylation of 6,7-dihydro-5//-dibenz[f,e]azepin-7-ones 2 and -7-thiones 5 with trimethyloxonium tetrafluo-roborate.181 iodomethane,181 or methyl trifluoromethanesulfonate.12 Treatment of the tri-fluoromethanesulfonates 3 and 6 (X = OTf), or the tetrafluoroborate 6 (X = BF4) with 2 M sodium hydroxide in dichloromethane liberates the free bases 4 and 7, respectively.7,181... 

Polar substituents have been attached to the porphyrin core in order to achieve water-solubility. (685) has been synthesized by reaction of the Ni11 complex of tetrakis(pentafluorophenyl)-porphyrin with dimethylammonium hydrochloride in DMF, followed by methylation with methyl trifluoromethanesulfonate (triflate) in trimethyl phosphate.1778 The triflate and chloride salts are... 

Bromoanlsole Anisole, o-bromo- (8) Benzene, 1-bromo-2-methoxy- (9) (578-57-4) Methyl trifluoromethanesulfonate Methanesulfonic add, trifluoro-, methyl ester (8,9) (333-27-7)... 

Acridine-9-carboxylic ester (100 mg) was dissolved in dichloromethane (5 mL). To this solution an excess of methyl trifluoromethanesulfonate was added. The mixture was stirred overnight at room temperature. Diethyl ether was added and the obtained precipitate was filtered, washed with diethyl ether, and dried. 

The synthesis of imidazo[2,Tc][l,2,4]triazolo-3-thiones has been investigated. For instance, the reaction of 1,2,4-triazoline-3-thione 361 <1995JHC275> with methyl trifluoromethanesulfonate affords the stable 3-methylmercapto-1,2,4-triazolium trifluoromethanesulfonate 362 in quantitative yield, which after treatment with sodium bicarbonate and bromine provides 6-bromomethyl-2,6-dimethyl-7-ethoxycarbonyl-2,3,5,6-tetrahydro-7//-imidazo[2,T4-[l,2,4]triazolo-3-thione 10 in 47% yield, via intermediate 363 (Scheme 36) <1996T791>. 

Alkylation or acylation takes place at the nitrogen in position 1 when l/7-[l,2,4]triazolo[4,3-A][l,2,4]triazole 9 is treated with methyl iodide or acetyl chloride, furnishing compound 10 or 11, respectively <1983S415>. The 7-methyl isomers 13 are obtained after conversion of compounds 9 into the 1-acetyl derivatives 11 followed by methylation with methyl trifluoromethanesulfonate to give the l-acetyl-6-aryl-7-methyl-3-methylthio-17/-[l,2,4]triazolo[4,3-A]-[l,2,4]triazol-7-ium-trifluoromethanesulfonates 12, which upon treatment with aqueous sodium carbonate afford the 7-methyl derivatives 13 <1985BCJ735>. 

Moreover, the sulfur atom of 1,4-oxathianes can be alkylated. Thus, reaction of 3-aryl-l,4-oxathianes 84 with (trimethylsilyl)methyl trifluoromethanesulfonate gave a mixture of cis- and /ra t-isomers of 3-aryl-4-(trimethylsilyl)-methyl-l,4-oxathianium triflates 85 (Equation 12) <1997J(P1)715>. 

Reaction of enolate 5 with methyl trifluoromethanesulfonate diastereoselectively provides 6 as may be expected, alkylation occurs from the less hindered face of the enolate opposite the phosphane ligand87. 

Related cations based on three- or four-membered polyphosphorus rings are obtained when sterically strained alkyl-substituted cyclo-tri- or -tetraphosphines are treated with methyl trifluoromethanesulfonate (MeOTf) or an in situ-generated phosphenium cation R2P (Scheme 11.2). ... 

Methyl triflate Methyl trifluoromethanesulfonate Methanesulfonic acid, trifiuoro-, methyl ester (8,9) (333-27-7)... 

Nitrones.1 O-Trimethylsilyloximes undergo N-methylation on reaction with Meerwein s reagent or methyl trifluoromethanesulfonate. The products are converted into nitrones on addition of KF or Bu4NF. Although both (E)- and (Z)-nitrones are formed initially, purification results in isolation of the more stable (Z)-nitrones. 

Methyl trifluoromethanesulfonate was purchased from Aldrich Chemical Company, Inc. 

The rapid aminolysis of cobalt(llI)-chelated glycine esters in aprotic solvents (Scheme 10 N4 = (en)2 or trien, R = Me, Et, R = H, CHR"C02Et) could be of value in peptide synthesis. The cobalt atom acts as both an N-protecting and an activating group. The synthesis of the chelated amino acid esters has presented some difficulties.207 A recent paper208 describes the use of methyl trifluoromethanesulfonate for the alkylation of chelated amino acids using dry trimethyl phosphate... 

Scheme 1. Abbreviations TFAA, trifluoroacetic anhydride DMF, N,N-dimethylformamide 2EHCOC1, 2-ethylhexanoyl chloride LAH, lithium aluminum hydride MeOTf, methyl trifluoromethanesulfonate.

Diphenyl-l,2,3-selenadiazole 138 and 3,5-diphenyl-l,2,4-selenadiazole 79 were alkylated with trimethylsilyl-methyl trifluoromethanesulfonate to give the salts 139 and 140 (Scheme 8) <2001J(P1)394>. Quaternizations occurred at N-3 and N-2, respectively. The structures and quaternization sites were confirmed by H, 13C, and 1SN NMR spectra and the subsequent reactions. The salts 139 and 140 were desilylated to generate transient selena-diazoliumylmethanide (ylide) intermediates. The transformation is described in Section 6.12.8. 

The reaction of triboracyclobutanide 36 in [D8]THF with methyl trifluoromethanesulfonate in an NMR tube at —90 °C affords a mixture of C-boryldiboracyclopropane 37 and compound 38 in a 3 1 ratio. Compound 36 reacts with dichloro(trimethylsilylmethyl)borane to give a product mixture, from which compound 39 (yield 50%) can be separated by crystallization (Scheme 2) <2003AGE671>. 

S-Alkylation of 6-aroyl-277-thiopyrans with alkyl iodides in the presence of either silver fluoroborate or dialkoxycar-benium fluoroborates in CH2C12 proceeds smoothly to afford the 1-alkylthiopyranium fluoroborates (Equation 108). Methyl trifluoromethanesulfonate proved more efficient for the S-methylation of 6-cyano- and 6-methoxycarbonyl-2/7-thiopyrans C1990TL115, 2001J(P1)2269>. 

Lithium butyltelluroselenolate is methylated by methyl trifluoromethanesulfonate. The butyl methylseleno tellurium is in equilibrium with dibutyl ditellurium and dimethyl diselenium2. 

The methylation of (/(-tellurido)bis[7t5-cyclopentadienyl(tricarbonyl)]chromium by methyl trifluoromethanesulfonate in diethyl ether at 20° produced a methyltelluro-bridged complex that was isolated as the hexafluorophosphatc2. The red-brown solid forms needles that are stable in air for a short time only. 

Dimethyl-l,3-benzotellurazolium Trifluoromethanesulfonate1 10.5 g (43 mmol) 2-methylbenzotelIura-zole are dissolved in 10 m) dry dichloromethane. 7.5 g (45 mmol) freshly distilled methyl trifluoromethanesulfonate are added. After a few min this exothermic reaction produces crystals, which are collected by filtration, washed with diethyl ether, and dried. The pale yellow powder is dissolved in 100 ml acetone. Diethyl ether is added, until the solution becomes turbid. Colorless plates separate upon cooling the turbid solution yield 87% m.p. 160-162°. 

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