Synthesis Of Non-phosphine Palladium Complexes And Their Catalytic Suzuki Coupling Of Polypseudohalogenated Compounds

The efficient construction of polyaromatic heterocycles by non-phosphine-palladium complexes catalyzed by polypseudohalogenation has been widely studied in the fields of pharmaceutical active molecules,bioactive molecules,polymers and functional materials.The previous phosphine catalytic systems have complex preparation and synthesis,low catalytic activity,air sensitivity,easy decomposition and high toxicity,and harsh reaction conditions,which are contrary to the concept of"green chemistry".Therefore,in recent years,researchers have turned their attention to non-phosphine ligands with high activity,low toxicity and easy preparation,which have become a hot spotin the field of ligand catalysis.In view of the above problems,this thesis designed and synthesized non-phosphine palladium complexes with different structures and used them to catalyze the Suzuki coupling reaction to construct the C-C bond.1.Five azacyclic carbene palladium complexes with different frameworks and ligands were designed and synthesized,and their structures were characterized by ¹H NMR and ¹³C NMR,and compared with their similar structures of azacyclic carbene palladium complexes.Exploring the effects of steric hindrance and electronic effects on catalytic activity and selectivity.In the catalytic reaction of chlorophenyl trifluoromethanesulfonate,the palladium complexes with suitable steric hindrance and electronic effect were screened,and the chemical selectivity of the reactants was reversed by changing different solvent systems.The experimental results show that the K1 with 4-diphenylmethyl-2-6-diethyl structure has the best effect.The N-aryl group is introduced into an ethyl group at the ortho position,and the substrate with moderate steric hindrance is more accessible to the palladium coordination center,and the electron donating ability of the ethyl group can also promote the oxidative addition reaction.Introducing a bulky sterically hindered benzhydryl group at the para position accelerates the elimination step and thus increases the reaction rate.Through the screening of reaction conditions,a series of coupling products with different substituents were synthesized.2.Threeα-diimine palladium complexes were synthesized to investigate their catalytic efficiency for the Suzuki coupling reaction of bromophenyl triflate and arylboronic acids.Among them,the large sterically hindered C1 with two benzhydryl groups shows the advantages of the highest reactivity and fast speed.In the air,using potassium carbonate as the base,isopropanol and water as the solvent,the corresponding coupling products can be obtained in good yields only at 80°C in 1 h.When the reaction temperature is lowered to 40°C,a series of coupling products can still be obtained in excellent yields by slightly prolonging the reaction time.And the obtained coupling product was further coupled with arylboronic acid using the K1 catalyst screened above.Three heterocyclic coupling products are obtained.3.In this paper,by changing the framework structure and ligands of the catalyst,the purpose of changing its electronic effect and steric hindrance effect is achieved,highlighting the importance of the design of N-aryl moiety substituents,framework structure and ligands,breaking the traditional catalyst The design concept of the structure,resulting in a series of aromatic heterocyclic coupling products.It provides a new idea for the design of metal catalysts and drug synthesis.