The Synthesis Of Phosphino-free Palladium Complexes And The Study Of Direct Arylation Reaction And Suzuki Coupling

Compounds containing aryl-aryl,aryl-heteroaryl or heteroaryl-heteroaryl structures can be synthesized by C-C coupling reaction.It has been widely applied in natural products,pharmaceuticals and materials.The direct C-H bond arylation and Suzuki coupling reaction are very efficient methods of C-C coupling,not only green,low cost,mild reaction conditions,and stable raw materials,easy to store.However,the ligands used to catalyze the above reactions are mostly phosphine ligands which are excellent in steric hindrance and electron effects,exhibiting good catalytic activity on C-C coupling reaction.But phosphine ligands are very poor in air Stable,and more toxic,therefore,the development of air stable and efficient phosphine-free ligand has become one of the hot spots of organic catalytic chemistry.1.In the second chapter,three bulky diimine palladium complexes were designed and synthesized.Their structures were characterized by 1H NMR and 13 C NMR,and X-ray single crystal diffraction of C1 and C3 was carried out.The effect of steric hindrance on the catalytic activity of the complex was investigated by increasing the steric hindrance.We found that the maximum steric hindrance of the diimine palladium complex C3 is the most effective precatalyst in the direct arylation,which can accelerate the the reduction elimination step and promote the whole catalytic cycle.2.In the three chapter,seven bulky Pd-NHC complexes were designed and synthesized.The structures of K1,K3,K4 and K6 were characterized by 1H NMR and 13 C NMR,and the structures of K1,K3,K4 and K6 were characterized by X-ray diffraction.Crystal diffraction.The effect of steric hindrance and electron effect on the catalytic activity of the complex was investigated by introducing a large steric group at the same time on the skeleton and the N-aryl moieties,while accelerating the Oxidation addition step and the reduction elimination step.The addition of a large ?-? conjugated acenaphthene skeleton enhances the ?-donate electron and increases the rate of oxidation addition.The addition of benzhydryl,which generate ?-? stacking effect with aryl chlorides to promote the oxidation of the addition step.We found that the N-heterocyclic carbene palladium complex K5 had the best activity in the Suzuki reaction,however,the K7 with the largest steric hindrance was poor in the catalytic performance,because the Isopropyl of o-position of N-aryl moieties resulting in the loss of flexibility and coordination of the complex,inhibiting the Oxidative addition step.Therefore,K5 was identitied as the most effective catalyst.3.Respectively catalyze the direct arylation of the five-membered heteroaryl bromides and its derivative,and the Suzuki reaction of the aryl / heteroaryl chlorides with aryl / heteroaryl boronic acid.The effects of steric hindrance,electron effect,alkali and solvent on catalytic performance and functional group tolerance were investigated.(1)Study on direct C-H bond arylation by ?-diimine palladium complexesThe results show that the palladium complexes C1-C3 can highly efficient for direct C-H bond arylation at C-2 position of the five-membered heteroarenes.The optimum reaction conditions were confirmed: C3(0.5-0.1 mol%),K2CO3(2.0 eq),DMAc as solvent,reaction at 130 oC for 12 h,and the GC yield was up to 99%.(2)Study on Suzuki coupling by N-heterocyclic carbene palladium complexesA series of coupling products such as aryl-aryl,aryl-heteroaryl or heteroaryl-heteroaryl were synthesized by K5 catalyzed Suzuki coupling reaction under aerobic conditions with inorganic weak bases.K5 was identitied as the most effective catalyst,the palladium loading can down to 0.025 mol%.The optimum reaction conditions were confirmed: K5 as catalyst,K2CO3 as base,anhydrous ethanol as solvent,reaction at 80 oC for 4h under aerobic conditions,and the GC yields was up to 99%.