The unexpected finding of the photocatalytic activity of Sc(OTf)3 prompted us to check our experiments thoroughly multiple times. We ensured that no organic impurities were driving the reaction. We also tested Sc(OTf)3 from different suppliers, but we found no significant variations except for reduced activity caused by traces of oxygen atom-containing solvents like MeOH, attributable to synthesis residues. This reduced activity could be improved by recrystallising Sc(OTf)3 from its solution in MeCN and using chloroform for precipitation. The photocatalytic activity could be ascribed to the weak absorption of Sc(OTf)3 in MeCN (this extended to the visible region around 400 nm), and it was also indicated by blue fluorescence with a distinct band at 505 nm observed upon excitation with 400 nm light (Fig. ).