Visible-Light-Driven Selective Oxidative Coupling of Amines to Imines by Bismuth-Rich Bismuth Oxybromide in Water.

Photocatalytic selective oxidative coupling of amines is a promising method for imine synthesis. Bismuth-rich bismuth oxybromide photocatalysts have been found to exhibit improved conversion and selectivity for the visible-light-driven selective oxidative coupling of amines to imines in water. Benzylamines with either electron-withdrawing or electron-donating groups undergo good conversion (94-99 %) and excellent selectivity (93-98 %) to the corresponding imines. The average apparent quantum efficiency at 455 nm is 57.4 %. Active species trapping experiments, isotope experiments, and in situ infrared spectroscopy reveal that water both serves as solvent and participates in the coupling reaction as a reactant. This work provides a green and environmentally friendly method for the efficient synthesis of imines with bismuth-rich bismuth oxyhalides and reveals water is involved in the oxidative coupling mechanism of benzylamines.