Redox-innocent scandium(III) as the sole catalyst in visible light photooxidations.

Abstract

In recent years, the catalytic activity of scandium triflate Sc(OTf)₃ has attracted significant attention due to its robust Lewis acidity and the oxophilicity of Sc³⁺. These features have led to impressive progress in developing diverse organic reactions, including C-C bond formation. The Sc³⁺ also facilitates single electron transfer in photoinduced reactions either by coordination to an organophotoredox catalyst, which modifies its redox reactivity, or by the formation of a scandium-superoxide anion complex after electron transfer from a light-absorbing redox-active compound. The prior consideration of Sc³⁺ as a redox-inactive/innocent metal ion initially hampered the investigation of the possibility of using Sc(OTf)₃ as a sole visible light photoredox catalyst. This work demonstrates the use of Sc(OTf)₃ as a visible light photocatalyst capable of direct and mild aerobic oxidative C-H functionalisation of aromatic substrates by oxidation of the benzylic position and direct cyanation of the aromatic ring.