Visible light-driven photocatalytic benzoyl azides formation from benzotrichlorides using rhodium ion modified TiO₂

Visible light-driven benzoyl azides formation catalyzed by a rhodium ion modified TiO₂ (Rh³⁺/TiO₂) is reported. The Rh³⁺/TiO₂ was prepared as a visible light responsive photocatalyst by a simple procedure from TiO₂ and RhCl₃･3H₂O. The Rh³⁺/TiO₂ exhibited a broaden visible light absorption from 400 nm to 600 nm. Benzoyl azide formation from a benzotrichloride and a trimethylsilyl azide (TMS-N₃) was performed catalyzed by the Rh³⁺/TiO₂ under visible light irradiation (λ ≥ 420 nm) in air at room temperature. In this reaction, the benzotrichloride was effectively reduced by the single electron transfer (SET) from the Rh³⁺/TiO₂, and the benzoyl azide was produced in 71% yield via the reaction between the benzoyl chloride and TMS-N₃. In addition, several benzotrichloride derivatives were applied to this reaction and the corresponding benzoyl azide derivatives were formed in up to 71% yield. A kinetic analysis was also performed on these reactions, and it was suggested that the SET is the rate determining step in this reaction.