Switching Copper(II)-Catalytic Process for the Selective Access to C3-Imidazolyl- and Pyridylquinoxalin-2(1 H )-ones

A simple pseudofour-component reaction catalyzed by CuBr₂ has been developed to deliver C3-imidazoylquinoxalinones with decent yields from quinoxalin-2(1H)-ones, acetophenones, and ammonium persulfate in DMSO. This process follows a sequence of cross-dehydrogenative coupling/Kornblum oxidation/aza-cyclization, creating selectively four new C-C, two C-N, and C═N bonds. Interestingly, the Kornblum oxidation step can be skipped by simply replacing CuBr₂ with Cu(OAc)₂. This alteration leads to high-value C3-pyridylquinoxalinones. Notably, DMSO serves both as a C-H source for pyridine ring synthesis and an effective solvent for this conversion. In addition, the acquired 3-imidazolyl- and pyridylquinoxalinones were transmuted into value-added 3-(imidazo[1,2-a]pyrazin-3-yl)quinoxalinone and 2-sulfonylquinoxalines, showcasing the synthetic utility of our method.