Copper-Catalyzed Domino Synthesis of 2-Imino-1H-imidazol-5(2H)-ones and Quinoxalines Involving C-C Bond Cleavage with a 1,3-Dicarbonyl Unit as a Leaving Group

Although 2-imino-1H-imidazol-5(2H)-ones have important biological activities in metabolism, their synthesis has rarely been investigated. Quinoxalines as privileged scaffolds in medicinal chemistry have been extensively investigated, but the development of novel and efficient synthetic methods remains very attractive. Herein, we have developed two copper-catalyzed domino reactions for the synthesis of 2-imino-1H-imidazol-5(2H)-ones and quinoxalines involving C-C bond-cleavage with a 1,3-dicarbonyl unit as a leaving group. The domino sequence for the synthesis of 2-imino-1H-imidazol-5(2H)-ones includes aza-Michael addition, intramolecular cyclization, C-C bond-cleavage, 1,2-rearrangement, and aerobic dehydrogenation reaction, whereas the domino sequence for the synthesis of quinoxalines includes aza-Michael addition, intramolecular cyclization, elimination reaction, and C-C bond-cleavage reaction. The two domino reactions have significant advantages including high efficiency, mild reaction conditions, and high tolerance of various functional groups.