Trifluoromethanesulfonic (triflic) Anhydride

Introduction

Trifluoromethanesulfonic (triflic) anhydride [(CF₃SO₂)₂O; Tf₂O] has proved to be a versatile reagent in organic synthesis over the last few decades. [1-3] Due to the excellent leaving group properties of the triflate group, Tf₂O finds its use in the conversion of various compounds to triflates which can be transformed into other useful products. Detailed studies have established triflates to be some 2 × 10 [4] to 2 × 10⁵ times more reactive than the comparable tosylates. [1]

The anhydride is best prepared by distillation of triflic acid from excess P₂O₅. [5] Stang found that yields can be considerably increased by using P₂O₅ premixed with an equal volume of celite. The pure anhydride is a colourless liquid that is stable for long periods, insoluble in water, does not fume in air and hydrolyses slowly over several days at room temperature. The liquid boils at 81 °C at 760 torr pressure. The reagent is also commercially available.

References

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