A New Simple And Effective Thiosemicarbazide Schiff Base Ligand For Copper(Ⅱ)-catalyzed C-N Coupling Reaction

Nowadays, Cu-mediated Ullmann-Glodberg is playing an important role in metal-mediated coupling reactions. However, until the beginning of the 21st century, this was certainly not the case, first reported a hundred years ago in the pioneering work of Ullmann and Glodberg. Even if these conceptual publications clearly are the basis of today'development of copper-mediated reactions, harsh reaction conditions and low substrate scope hampered the application of industy and academy fields. In a long time, palladium-catalyzed transformation were prefered in the most cases. This situation has come to an end with the prosperous development, in the past 10 years or so, of highly efficient copper/ligands catalysis system that allow reactions to be conducted in milder conditions and with dramatically enhanced yield compared to classical procedures.C-N coupling reactions, for the synthesising of the medications, dyes and materials, are consider as a highlight of Ullmann-type coupling reactions. Herein, a new methodology of copper-catalyzed coupling reaction has been developed, using Cu(II) as catalyst and thiosemicarbazide Schiff bases as ligands.Firstly, author designed an sample reaction, for the screening of individual reaction parameters, including three ligands and three solvents, which imidazole and 3-iodo-nitro-benzene are chosen as two available substrates. In the results, L/Cu(II) systems received 76～83% yield demonstrate they are the better combination rather than L/Cu(I) only gave 63～67% yield.Secondly, Base on the work has been descriped in the last chapter, we further extended the reaction scope and examined the influence of substrates of the reaction with 11 pair of substrates. Then, up to these work, the probably mechanism was figured out and expatiated.Finally, with the established methology in the 2nd chapter, author tried another type substrates, using acylamides reacted with aryl halides. Here, we synthesised a new ferrocene thiosemicarbazone ligand, besides the 3 used ligands. Subsequently, an adapt catalysis system was established for the coupling reaction between caprolactam and 3-iodio-nitrobenzene with 79% yield.In conclusion, firstly, we offered a series simple, efficient and low-toxical copper ligands for the Ullmann-Glodberg coupling reactions; Secondly, the researching results demonstrated it is the first time that the new ligands were chelated with copper(Ⅱ), which showed better catalytic effect than those copper(Ⅰ) catalysts. Since the stability and economy of copper (Ⅱ), this methodology will be a promising approach in copper-catalyzed C-N formation reactions. Finally, about 12 important ligands and products were clearly confirmed by 1H NMR and 13C NMR.