Triflic Acid

Introduction

Trifluoromethanesulfonic acid (TfOH), more commonly named triflic acid, is one of the strongest Brønsted acids and well known as a ‘super acid’ with a pK_a of –13.6. The reagent is a colorless liquid and stable towards heating, oxidation and reduction. It was first synthesized in 1954 by Haszeldine and Kidd by oxidation of bis(trifluoromethylthio)mercury with aqueous hydrogen peroxide.[ ¹ ] It is available on an industrial scale and is produced by electrochemical fluorination. Triflic acid is an effective reagent widely used in organic chemistry and especially as catalyst (historically for esterification and salt formation),[ ² ] even if more than one equivalent is often used.[ ³ ] However, its utilization mainly includes addition to α-carbonylated alkynes,[ ⁴ ] hydrogenation,[ ⁵ ] Friedel–Crafts reaction,[ ⁶ ] polymerization,[ ⁷ ] cycloaddition,[ ⁸ ] deprotection,[ ⁹ ] initiation of cyclisation sequences,[ ¹⁰ ] and as a counterion both for iodonium salts[ ¹¹ ] and N-heterocyclic carbenes.[ ¹² ]

• References

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