Addition reactions trifluoromethanesulfonic anhydride

The reaction was performed in flame-dried modified Schlenk (Kjeldahl shape) flask fitted with a glass stopper or rubber septum under a positive pressure of argon. Trifluoromethanesulfonic anhydride (1.4 equiv) was added to a solution of giycosyl donor (0.191 mmol, 1 equiv) and diphenyl sulfoxide (2.8 equiv) in a mixture of toluene and dichloromethane (8 ml, 3 1 vol/vol) at — 78 °C. The reaction mixture was stirred at this temperature for 5 min and then at —40 °C for 1 h. At this time, 2-chloropyridine (5.0 equiv) and the giycosyl acceptor (3.0 equiv) were added sequentially at —40 °C. The solution was stirred at this temperature for 1 h, then at 0 °C for 30 min and finally at 23 °C for lh before the addition of excess triethylamine (10 equiv). The reaction was diluted with dichloromethane (100 ml) and was washed sequentially with saturated aqueous sodium bicarbonate solution (2 x 100 ml) and saturated aqueous sodium chloride (100 ml). The organic layer was dried (sodium sulfate) and concentrated. The residue was purified by silica gel flash column chromatography. 

To a solution of thioglycoside (1.0 equiv), 1-benzenesulfinyl piperidine (1.0 equiv), TTBP (2.0 equiv), and freshly activated 3 A powdered molecular sieves in dichloromethane (25.0 ml mmol-1) was added trifluoromethanesulfonic anhydride (1.1 equiv) at —60 °C under an argon atmosphere. The reaction mixture was stirred for 5 min, after that a solution of the glycosyl acceptor (1.5 equiv) in dichloromethane (4.0 ml mmol-1) was added. The reaction mixture was stirred at — 60 °C for 2 min, after that it was slowly warmed to room temperature and quenched by the addition of saturated aqueous NaHC03. The organic layer was washed with brine, dried (MgS04), filtered and the filtrate was concentrated to dryness. Purification of the crude product by column chromatography over silica gel afforded the product. 

The perchloric acid catalyzed acylation of selenophene with acetic anhydride is claimed to give solely 2-acetylselenophene <81MI 2l3-0l>. Ethoxalyl chloride reacts at the same position <83BEP896054>. Reaction with trifiuoromethylsulfenyl chloride and stannic chloride gives 2-trifluoromethylthioselenophene, and addition of trifluoromethanesulfonic acid promotes formation of the 2,5-bis(trifluoromethylthio) derivative <83JFC(23)525>. 

An alternative approach to benzo[Z ]thiophene derivatives includes treatment of an aryl-substituted ketene dithioacetal monoxide 188 with trifluoromethanesulfonic anhydride [99] (TfjO) in the presence of K2CO3 in toluene at 25 °C, followed by addition of ethanolamine to the reaction mixture, provided benzo[fc]thiophenes, including 3-trifluoromethylbenzo[Z ]thiophene 189, in good yields. The cyclization proceeded through formation of reactive sulfonium electrophile [1(X)]. The synthesis of the starting material 188 was also facile and scalable, starting from aryl ketone 186 and formaldehyde dimethyl dithioacetal S-oxide (FAMSO) [101]. 

Preparative Method trifluoromethanesulfonic anhydride (17 mL, 0.100 mol) in benzene (20 mL, 0.220 mol) was added to a suspension of sodium trifluoromethanesulhnate (6.98 g, 44.7 mmol) in dichloromethane (5 mL) at 0 °C. After vigorously stirring at 0 °C for 1.5 h, the reaction mixture was warmed to room temperature and mixed for an additional 34 h. The reaction mixture then was diluted with CH2CI2 (150 mL), washed with saturated aq. NaHCOs and saturated brine, and dried over Na2 SO4. After concentration under reduced pressure, the residue was purihed by column chromatography on silica gel using dichloromethane/acetonitrile (4 1) as the eluent. 

A. 3-Butyn-l-yl Trifluoromethanesulfonate. A 500-ml., three-necked flask is fitted with a mechanical stirrer, a pressure-equalizing dropping funnel, and a stopper. The system is flushed with nitrogen through a gas-inlet tube attached to the top of the funnel. To 150 ml. of dry methylene chloride (Note 1) in the flask is added 75 g. (0.27 mole) of trifluoromethanesulfonic acid anhydride (Note 2), and the solution is cooled to —40°. After addition of 14.5 g. (0.14mole) of finely powdered anhydrous sodium carbonate (Note 3), 15 g. (0.21 mole) of 3-butyn-l-ol (Note 4) is added dropwise over a 20-minute period to the well-stirred reaction mixture maintained at —40° to —55°. Stirring is continued at —30° for 2 hours and then at 0° for another hour, and finally the... 

Friedel-Crafts Reactions. Aluminum trifluoromethanesulfonate has been used for the Friedel-Crafts alkylation reaction of toluene with isopropyl and tert-butyl chlorides (eq 1), and for the acylation of benzene and toluene with acetyl and benzoyl chlorides in low to moderate yields. Intramolecular Friedel-Crafts acylation of an aromatic compound with Meldrum s acid has also been reported using catalytic amounts of Al(OTf)3. Acylation of 2-methoxynaphthalene with acetic anhydride has been reported using Al(OTf)3 and lithium perchlorate as an additive to afford the corresponding 6-acetylated adduct in 83% yield. Effective acylation of arenes with carboxylic acids has also been disclosed using polystyrene-supported Al(OTf)3. ... 

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