Development of a copper-chelated ZIF-67 framework to effectively catalyse oxidative coupling between N-arylmaleimides and N,N-dimethylanilines

Producing bioactive skeletons through direct oxidative coupling of C(sp3)-H bonds adjacent to heteroatoms with C(sp2)-H alkenes bonds has become a topic of growing interest, in which catalysts play an important role. However, designing an effective and stable catalyst for these coupling reactions remains a great challenge. The Cu@ZIF-67 material, in which Cu(II) species were chelated into the 2-methylimidazole moiety of the ZIF-67 framework, was prepared and used as a catalyst in an oxidative coupling reaction between N-phenylmaleimide and 4,N,N-trimethylaniline. Cu@ZIF-67 was characterized using X-ray powder diffraction (PXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and thermal gravimetric analysis (TGA). Gas chromatography (GC), 1H NMR, and 13C NMR were employed to determine the yield and chemical structure of the product. The Cu@ZIF-67 material exhibited remarkable catalytic activity by increasing the product yield to 93% under optimal reaction conditions. In addition, various tetrahydroquinoline derivatives were produced using Cu@ZIF-67 as a catalyst. It was found that the high catalytic activity of Cu@ZIF-67 resulted from the synergistic effect of the chelated Cu species and ZIF-67 structure. This work provides a promising catalyst for different organic syntheses.