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

Abstract 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 AlCl 3 , BF 3 , and SnCl 4 , 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 (Sc 3+ ), 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.