Triflimide (HNTf₂) in Organic Synthesis

Triflimide (HNTf₂) is a commercially available and highly versatile super Brønsted acid. Owing to its strong acidity as well as good compatibility with organic solvents, it has been widely employed as an exceptional catalyst, promoter, or additive in a wide range of organic reactions. On many occasions, triflimide has been demonstrated to outperform triflic acid (TfOH). The uniquely outstanding performance of triflimide also benefits from the low nucleophilicity and noncoordinating property of its conjugate base (Tf₂N^-). Therefore, it has been employed as a precursor toward a variety of cationic metal complexes or organic intermediates with enhanced reactivity or catalytic activity. In this Review, we describe these features and applications of triflimide in organic synthesis, including its synthesis, physical properties, and role as catalyst or promoter in organic reactions. At the end of this Review, another closely related reagent, triflidic acid (HCTf₃), is also briefly introduced.