Unprecedented Selective Synthesis of Imines by Photocatalytic Oxidative Coupling of Primary Amines under N₂O Atmosphere

In a climate change context, N2O contributes to global warming with CO2 and CH4. As an inert molecule, its upgrading as oxidant still constitutes a challenge in chemical synthesis. Here, the synthesis of imines was unprecedently performed using nitrous oxide (N2O) as a novel and highly selective oxidative agent for the photocatalytic homo-coupling of amines. In a similar way, unsymmetric imines were produced through cross-coupling of amines with alcohols. Promisingly, this greenhouse gas showed excellent performances towards the target reactions when photocatalytically activated at atmospheric pressure, with silver photodeposited on titanium dioxide as catalyst. Relevantly, reactions under N2O atmosphere exhibited high conversion rates and turn-over frequencies, and higher selectivities than the ones carried out under a dioxygen atmosphere. Mechanisms for both reactions were detailed, showing the release of nitrogen and water as benign by-products.