Trifluoromethanesulfonic anhydride


Triflic anhydride is the chemical compound with the formula 2O. It is the acid anhydride derived from triflic acid. This compound is a strong electrophile, useful for introducing the triflyl group, CF3SO2. Abbreviated Tf2O, triflic anhydride is the acid anhydride of the strong acid triflic acid, CF3SO2OH.

Preparation and uses

Triflic anhydride is prepared by dehydration of triflic acid using P4O10.
Triflic anhydride is useful for converting ketones into enol triflates.
In a representative application, is used to convert an imine into a NTf group. It will convert phenols into a triflic ester, which enables cleavage of the C-O bond.

Assay

The typical impurity in triflic anhydride is triflic acid, which is also a colorless liquid. Samples of triflic anhydride can be assayed by 19F NMR spectroscopy: −72.6 ppm vs. −77.3 for TfOH.

Safety

It is an aggressive electrophile and readily hydrolyzes to the strong acid triflic acid.