Visible Light-Driven Catalytic Synthesis of N -Formamides from Secondary Amines by Metal Ion-Modified TiO 2

A novel and environmentally benign approach for the synthesis of N -formamides from secondary amines under mild conditions, using visible light and atmospheric oxygen as the sole atomic sources is reported. The reaction is efficiently catalyzed by metal ion-modified titanium dioxide (M n+ /TiO 2 ) 1,2 , a cost-effective and non-toxic photocatalyst. Among the M n+ /TiO 2 , Cu 2+ -modified TiO 2 exhibited the highest efficiency. Notably, this method eliminates the need for additives, high pressures, or hazardous reagents, offering a highly sustainable alternative to traditional N -formylation strategies. Mechanistic investigations revealed that the reaction proceeds via an enamine intermediate, which subsequently forms a dioxetane intermediate. The decomposition of dioxetane leads to N -formamide formation. Isotope-labeling experiments and DFT calculations confirmed that the oxygen atoms in the final product originate from molecular oxygen in the air. This strategy not only establishes a direct and green synthetic route to N -formamides but also expands the potential of visible-light-driven photocatalysis in sustainable organic transformations. References 1. K. Shichijo, H. Shimakoshi et al., Chem. Eur. J . 2025 , 31 , e202403663. 2. Md. Hossain, H. Shimakoshi et al., Chem. Eur. J . 2025 , 31 , e01845. Figure 1