Eosin Y-catalyzed photo-induced direct C(sp2)-H bond azo coupling of imidazo-heteroarenes and anilines with aryl diazonium salts.

Herein, a greener approach to the eosin Y-Na-2 catalyzed, C(sp(2))-H bond azo coupling of imidazoheteroarene with aryl diazonium salts is described, under acid free conditions. This direct photoredox process resulted in the corresponding azo products in good to excellent yields. Besides, this new approach could also be applicable to anilines, which is a poorly reactive substrate by other methods. The main features of this reaction are that it provides high yields and is gram-scalable and applicable to biologically relevant imidazoheteroarenes and -anilines.