Development and Scale-Up of a Novel Photochemical C–N Oxidative Coupling

A visible light promoted C–N-coupling of a functionalized pyridazinone with veratrole was developed to forge the central C–N bond of an agrochemical intermediate. Dosing aqueous NaOCl and 4% O₂ in N₂ under blue light irradiation (460 nm) was key to promote the desired transformation while generating benign wastes. Mechanistic studies suggest the formation of a N-chloro species that undergoes selective coupling via a radical pathway induced by the combination of light and oxygen. Further development led to an optimized semi-batch process, which was successfully scaled up to an initial 20 L and then 1.2 m³.