CuMgAl hydrotalcite as an efficient bifunctional catalyst for the cross-dehydrogenative C-C coupling reactions under mild conditions

CuMgAl layered double hydroxide compounds (CuMgAl-LDHs) have been synthesized, characterized and in-vestigated in the aerobic CDC reactions. The results indicated that NH3 center dot H2O coprecipitated CuMgAl LDH (N-CuMgAl-LDH) was able to efficiently accelerate the CDC reactions between the alpha-Csp(3)-H of N-aryltetrahy-droisoquinolines and nucleophiles. A wide scope of N-aryltetrahydroisoquinoline analogues and nucleophiles with different C-H bonds (C-sp3-H, C-sp2-H and Csp-H) could be tolerated by the N-CuMgAl-LDH system. Compared with the sample using Na2CO3 as the precipitant (C-CuMgAl-LDH), N-CuMgAl-LDH showed higher catalytic activity, which probably was due to its higher surface acidity. Dual function of redox and acidity for the N-CuMgAl-LDH catalyst has been observed in the CDC reaction. According to the obtained catalytic results, kinetic isotope effect experiment and XPS analysis, iminium ion was proposed as the key intermediate, made possible by the cycle of Cu2+ and Cu+ under the aerobic conditions.