The Synthesis Of Nitroheterocyclic Carbene Palladium And Its Catalyzed Suzuki Coupling Reaction

The Aromatic（hetero）ring-aromatic（hetero）ring structure constructed by C-C bonds are widely used in natural products,materials,pharmaceutical research,development and pesticides.These structures can be palladium-catalyzed Suzuki coupling reaction Get built efficiently.At present,the Suzuki coupling reaction catalyzed by palladium has received great attention.The traditional catalytic system is unstable to the air during the above reaction,the environmental pollution is more serious,the preparation process is cumbersome and generally has greater toxicity,which greatly limits its large-scale development.On the other hand,non-phosphine palladium catalysis is relatively Phosphine ligands have the advantages of air stability,high catalytic activity,low toxicity,and no pollution to the environment.Therefore,the development of high-efficiency,low-toxicity,air-stable non-phosphine ligands and their palladium complexes has become a hot spot in the field of organic chemical catalysis.1.Designed with fivedifferent spatial resistance and electron effects of the anthracene carboned palladium complex,the structure is characterized by ¹H NMR and ¹³C NMR,and the effects of electron effect and bit-resistance should be in the catalytic efficiency.the catalyst precursor is investigated by combining the original nitrogen heterocyclic carbene palladium complexes in the laboratory to establish a model reaction.Chemoselectivity is restricted by various conditions such as ligands,solvents,and temperature.A ligand with adequate steric hindrance and electronic effects is synthesized.The use of two solvent systems alone can change the chemical selectivity of the substrate.Finally,it was found that K21 is the best catalyst.Its N-aryl group introduces the structure of the ortho-position substituent of the electron-donating group,and the para-position introduces a strong electron withdrawing group.The mutual restriction between the two makes the ligand electronic effect promote Oxidative addition step.However,if the steric hindrance is too large or too small,it will affect the catalytic activity and selectivity.There is also a benzhydryl group in the N-aryl group.Increasing the steric hindrance is beneficial to speed up the reduction and elimination step and improve the catalytic activity.Therefore,the two optimal reaction conditions of the system were determined,and a series of（hetero）ring-aromatic（hetero）compounds with high efficiency and chemoselectivity were obtained.2.Designed three kinds of nitrogen heterocyclic carbene palladium ligands with simple synthesis and readily available raw materials for the Suzuki coupling reaction of organic sulfide diphenyl sulfoxide and boric acid,and carried out nuclear magnetic characterization to evaluate the electronic effect And steric effect,the structure shows that the introduction of methyl into the structure of the classic carbene catalyst ligand will make the ligand have a stronger electron donating ability,thereby accelerating the oxidation addition rate in the catalytic reaction,the steric hindrance of K26 and the strong electron donating.The group has the best activity for Suzuki coupling reaction.Using a mixed solvent of tetrahydrofuran and water,using K₃PO₄ as a base in the air,and efficiently catalyzing the Suzuki reaction of diphenyl sulfoxide at 70℃,a series of coupling products were obtained.3.In this paper,the structure design of the N-aryl part and the skeleton part of the nitrogen heterocyclic carbene palladium ligand,so that the electronic effect and steric effect of the ligand can be changed,and the polyhalogen（pseudo）compound can be controlled by controlling the solvent or temperature.The selectivity provides a new approach.This concept breaks the traditional concept of catalyst structure design and provides a new idea for other researchers in this field in the design and synthesis of metal-catalyzed ligands.