Recent Advances in Scandium(III) Triflate Catalysis: A Review

Over the past three decades, triflate salts have emerged as crucial Lewis acid catalysts in organic synthesis, playing a significant role in cyclization, C‐H bond functionalization, and various other reactions. Among these, rare‐earth triflates have garnered attention due to their water compatibility, environmental friendliness, noncorrosive nature, and reusability. In particular, scandium(III) triflate [Sc(OTf)3] stands out as a water‐resistant Lewis acid with remarkable catalytic activity in aqueous environments. Unlike typical Lewis acids such as AlCl3, BF3, and SnCl4, which are decomposed or deactivated by water, Sc(OTf)3 remains stable and effective. Its exceptional Lewis acidity, resilience against hydrolysis, and recyclability make it a prominent green catalyst. The unique stability of Sc(OTf)3 in water is attributed to the smaller size of scandium ions (Sc3+), enhancing its catalytic efficiency. Sc(OTf)3 has a longstanding history in organic synthesis, facilitating a wide range of reactions including aldol, Michael, allylation, Friedel‐Crafts acylations, Diels‐Alder, Mannich, cycloadditions (including cyclopropanation), and cascade reactions. The increasing utilization of Sc(OTf)3 over the past decade underscores the necessity for updated insights. This review provides a concise overview of the versatility of Sc(OTf)3 as a catalyst, focusing on developments from 2017 to 2024.