Pyridines trifluoromethanesulfonic anhydride

Trifluoromethanesulfonates of alkyl and allylic alcohols can be prepared by reaction with trifluoromethanesulfonic anhydride in halogenated solvents in the presence of pyridine.3 Since the preparation of sulfonate esters does not disturb the C—O bond, problems of rearrangement or racemization do not arise in the ester formation step. However, sensitive sulfonate esters, such as allylic systems, may be subject to reversible ionization reactions, so appropriate precautions must be taken to ensure structural and stereochemical integrity. Tertiary alkyl sulfonates are neither as easily prepared nor as stable as those from primary and secondary alcohols. Under the standard preparative conditions, tertiary alcohols are likely to be converted to the corresponding alkene. 

Activated amides have been generated by using trifluoromethanesulfonic anhydride in the presence of pyridine and been thionated with 20 wt% aqueous solution of ammonium sulfide to afford the desired secondary or tertiary thioamides in high yields (Scheme 13).34... 

The third procedure illustrated by this preparation involves the reaotion of ketones with trifluoromethanesulfonic anhydride in a solvent such as pentane, methylene chloride, or carbon tetrachloride and in the presence of a base such as pyridine, lutidine, or anhydrous sodium carbonate.7-11,15 This procedure, which presumably involves either acid-catalyzed or base-catalyzed enolization of the ketone followed by acylation of the enol with the acid anhydride, has also been used to prepare other vinyl sulfonate esters such as tosylates12 or methanesulfonates.13... 

Sonogashira coupling of acetylenes with 24 and with the triflate 25 have also been reported (Equation 11) <2003RCB441>. The latter substrate is formed by treatment of the trione 26 with trifluoromethanesulfonic anhydride and pyridine chloride and triflate are comparable in respect of cross-coupling yields. 

A solution of 5,7-dihydroxyflavone (10 g) dissolved in 200 ml CH2C12 was treated with 12.7 ml pyridine followed by 6.6 ml of trifluoromethanesulfonic anhydride, then stirred 3 hours at 0°C. The mixture was neutralized with 1M HC1 and extracted with CH2C12. The extract was concentrated and the product isolated in 92% yield as a white powder. 

The conversion of bisphenol 19 to the corresponding bistriflate 20 is performed by treating 19 with trifluoromethanesulfonic anhydride (Tf20) in the presence of pyridine. 

Chlorophenol, trifluoromethanesulfonic anhydride, and anhydrous pyridine were purchased from Aldrich Chemical Company, Inc., and used without further purification. 

The highly reactive trifluoromethylsulfonyloxy (triflate) group is introduced into malate esters by treatment of 2 or 3 with trifluoromethanesulfonic anhydride at —78 °C in the presence of 2,6-lutidine [70,71,72], or at 0 °C in the presence of pyridine [73]. Yields are generally high, often exceeding 90%. Triflates 197 can be generated in situ, and need not be isolated. 

Allyl triflate, CHa CHCHaOSOaCFa (1). Mol. wt. 191.16, colorless liquid, must be stored at —78° in a vented flask. This triflate can be prepared in pure form in 69yo yield by the reaction of allyl alcohol with trifluoromethanesulfonic anhydride and pyridine in dichloromethane. ... 

Apart from aryl halides, other very easily available substrates for nickel-catalysed biaryl (II) synthesis are aryl sulfonates (XII). Method D is very efficient in the homocoupling reactions of substituted aryl sulfonates in good to excellent yields [15], Table 6. Substituted aryl sulfonates are readily obtained from phenols and trifluoromethanesulfonic anhydride, benzenesulfonyl-, tosyl- or methanesulfonyl chloride in pyridine, or in a suitable inert solvent such as dichloromethane in the presence of triethylamine or Hiinig s base. Among other nickel complexes, Ni(dppe)Cl2 and Ni(dppf)Cl2 have been used (10 mo1%) as slightly less versatile catalysts for the homo-couplings of naphthyl sulfonates in refluxing THF, DMF or their mixtures [42]. 

The desired sulfonate ester is usually prepared by reaction of the alcohol in pyridine with the appropriate sulfonyl chloride, that is, methanesulfonyl chloride (mesyl chloride) for a mesylate, y)-toluenesulfonyl chloride (tosyl chloride) for a tosylate, or trifluoromethane-sulfonyl chloride [or trifluoromethanesulfonic anhydride (triflic anhydride)] for a triflate. Pyridine (C5H5N, pyr) serves as the solvent and to neutralize the HCI formed. Ethanol, for example, reacts with methanesulfonyl chloride to form ethyl methanesulfonate and with yj-toluenesulfonyl chloride to form ethyl /-toluenesulfonate ... 

Trifluoromethanesulfonates of alkyl and allylic alcohols can be prepared by reaction with trifluoromethanesulfonic anhydride in halogenated solvents in the presence of pyridine. ... 

Other Uses. Imidazole is one of the best catalysts for the preparation of acid chlorides from the corresponding carboxylic acids and phosgene. Aryl triflates can be obtained from phenols, or better phenolates, using Trifluoromethanesulfonic Anhydride in combination with imidazole A-triflylimidazole is the reactive species. Photochemical deconjugations of enones can be erratic but are promoted by the presence of a weak base such as imidazole or pyridine in polar solvents. ... 

Methyl 4,6-0-benzylidene-3-0-methyl-/ -D-mannopyranoside (1.33 g, 0.45 mmol) was dissolved in CH2C12 (5mL) and pyridine (0.11 mL, 1.3 mmol) and the solution was cooled in an ice-salt bath. Tri-fluoromethanesulfonic anhydride (0.20 mL, 1.2 mmol) was added dropwise (the TLC indicated that the reaction was complete in less than 10 min). The mixture was washed sequentially with ice-cold, dil HC1 and H20, dried (MgS04), and evaporated to give the corresponding trifluoromethanesulfonate derivative, which was taken up in CH2CI2 (5 mL). TASF (0.42 g, 1.37 mmol) was added to this CH2C12 solution whilst the vessel was cooled by an ice salt bath. The vessel was removed from the cooling bath and, after... 

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