Triflating agents

Vinyl Inflates are especially attractive in Stille reactions since they can be prepared regioselectively from enolizable ketones by trapping the enolate oxygen with triflating agents (e.g., Tf20, PhNTf2 ). For reactions of vinyl triflates with... 

Triflation. This stable, crysu triflating agent for phenols. 

Phenyltrifluoromethanesulfonimide (Tf2NPh) is widely used to triflate alcohols and amines. As a milder triflating agent compared to triflic anhydride (Tf20), it proves to be useful for the selective formation of triflates. A primary alcohol was transformed into its triflate in the presence of a secondary alcohol and subsequently reacted to form an oxetane of the desired stereochemistry (eq 9). Inflation of a secondary over a tertiary alcohol allows dehydration to form a conjugated olefin (eq 10). Tf20 induced partial decomposition in this case. ... 

Pyridine can become involved in nucleophilic substitution when very reactive trifiates are being synthesized. One approach to minimize this disadvantage is to replace it with sterically hindered bases, such as 2,6-di-f-butyl-4-methylpyridine, 2,4,6-trisubs-tituted pyrimidines, or nonnucleophilic aliphatic amines (usually W,W-diisobutyl-2,4-dimethyl-3-pentylamine). No salt formation appears to take place under these conditions. The triflic anhydride seems to be the direct triflating agent and the base only neutralizes the triflic acid formed. Numerous alkyl triflates have been prepared in the literature by the above method. Some recent examples of triflates prepared from alcohols are illustrated in eqs 2 and 3. As an exception, 2,6-dinitrobenzyl alcohol does not react with Tf20 although similar sulfonyl esters could be prepared. ... 

Aniline allowed to react at -78° with trifluoromethanesulfonic acid anhydride and triethylamine in methylene diloride -> N-phenyltriflamide. Y 97%. - The protective group can be removed by reduction. F. e. and triflating agent, also Gabriel-type synthesis of prim, amines from halides via triflamides, s. J. B. Hendrickson and R. Bergeron, Tetrah. Let. 1973, 3839. 

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