Phosphino-free Palladium Complex Catalyzed Reductive Heck Reaction And Suzuki Coupling Reaction

The?hetero?aryl-?hetero?aryl and alkylated arenes were found in numerous applicaiton in medicine,agricultural chemicals,natural products,and photovoltaic materials.Among them,the Csp²-Csp² and Csp²-Csp³ bonds could be constructed by palladium-catalyzed Suzuki cross-coupling reaction and reduced Heck coupling reaction.In previous,the frequently used phosphine ligands were turned out to be toxic and sensitive toward air,As the environment is seriously be concerned and the reaction conditions are generally harsh,and therefore limiting their large-scale applications.The development of phosphine-free ligands,which featured in air-stable,environmental-friendly and highly catalytic efficient toward transformation,has received much attention in recently decades.1.In the thrid chapter,six?-diimine palladium complexes were synthesized and their structures were fully characterized by 1H NMR and¹³C NMR.Moreover,the X-ray single crystal diffraction of K1 and K4was performed.The effects of electronic and steric hindrances on catalytic efficiency were explored.It was revealed that large sterically hindered ligands can protect Pd-H intermediates and inhibit the elimination of?-hydrides,However,when the rigid steric hindrance introduced,the reactoin efficiency was decreased.The result indicated that the bulky-yet-flexible ligand favor the reductve Heck reaction.The flexibility of the palladium complex can promote the oxidative addition process and promote the 1,2-insertion of olefins,while the bulky steric will accelerate the reductive process Among these palladium precatalyst evaluated,the K4,which is readily synthesized,was proved to be the optimal precatalyst.It afforded highly selective reductive Heck coupling products and the side reaction was suppressed.Upon the optimal reaction conditions,the substrate was expanded and a series of coupling products were synthesized.2.In the second chapter,five NHCs palladium ligands were synthesized and used in the Suzuki cross-coupling reaction of aryl chloride,and their chemical structures were characterized by ¹H,¹³C NMR,and X-ray single crystal diffraction.The electronic and steric effect was evaluated.The TEP effect demonstrated that the introducing dianisole structure into the skeleton lead to strong electron-donating ability,thereby it will accelerate the oxidative addition rate in the catalytic reaction.Moreover,the%Vbur revealed that C4 was bulky-yet-flexibile.The suitable steric hindrance and strong electron-donating ability of C4 showed highest catalytic efficiency for the Suzuki-Miyaura cross-coupling reaction.It is quite importance that using a THF/H₂O mixed solvent,the reaction would be smoothly proceeded under the temperature of 60°C in the presence of K₂CO₃ in air.Under these optimal reaction conditions,the substrate was expanded and a series of coupling products were synthesized.3.The electronic and steric effects of the ligand can be controlled by changing the backbone structure,this thesis emphasized the importance of incorporating both the backbone and N-aryl moieties in catalyst design,and provide new direction for other researchers in the field of catalysis and organic chemistry.