Study On Chan-Lam Coupling Reaction Catalyzed By Copper-containing COFs And MOFs

Nitrogen-containing heterocyclic compounds and amine compounds are closely related to industry and human life,including in medicine,polymer materials and chemical production.At present,the most widely used method is the use of transition metal catalysts to catalyze the synthesis of C-N bonds.Among them,homogeneous copper-catalyzed Chan-Lam coupling reaction has received widely attention recent years because of its relatively mild reaction conditions and tolerance of various functional groups.However,the homogeneous catalytic system has difficulty in separating and recovering catalysts.Therefore,the preparation of heterogeneous copper catalysts for the Chan-Lam coupling reaction is a research direction with great practical application prospects.Metal organic frameworks?MOFs?and its derivatives covalent organic frameworks?COFs?are two types of porous framework materials based on organic molecular building blocks with highly regular pore structure,which can be pre-designed and modified.Imine-based Covalent Organic Frameworks have high chemical and thermal stability,which can be used as a support for copper catalysts in Chan-Lam coupling reaction.We prepared a COF material TpBpy with a two-dimensional layered structure containing bipyridine sites by solvothermal method and realized the functionalization by modifying the copper salt after the bipyridine site on the ligand.Then powder X-ray diffraction,Fourier transform infrared spectroscopy,thermogravimetric analysis,nitrogen adsorption-desorption experiments and other methods were used to characterize the structure.We then investigated the catalytic performance of the obtained Cu@TpBpy in Chan-Lam coupling reaction of phenylboronic acid and imidazole.By optimizing the reaction conditions such as solvent,copper source,base and reaction time,we found that the reaction yield is highest when using the protic polar solvent MeOH,while Cu?OAc?₂·H₂O has the best catalytic effect among various copper sources and the soluble organic triethylamine?TEA?has the highest catalytic activity.As a result,Cu?OAc?₂·H₂O@TpBpy catalyzed the reaction of imidazole with phenylboronic acid at 70?for 4h under the promotion of base TEA in MeOH achiving the maximum yield of the target product 1-phenylimidazole which was 66%.The substrate expansion experiments was carried out under the optimal reaction conditions.The results showed that the steric hindrance effect of the substituents had a significant effect on the catalytic system.The yield of 4-chlorophenyl boronic acid with para-substituents was the highest?62%?.We further investigated the catalytic performance of a series of copper-containing MOFs and COFs materials with good chemical stability,including Cu?OAc?₂@CTF-1 prepared by post-modification and two copper-based metal organic frameworks?MOFs?MOF-199 and Cu/ZIF-67.In the coupling reaction of phenylboronic acid and imidazole,the yields of 1-phenylimidazole catalyzed by Cu?OAc?₂@CTF-1,MOF-199 and Cu/ZIF-67 are 58%,45%and 59%,respectively under optimal conditions.The results showed that the copper-based catalyst stabilized by nitrogen-containing heterocyclic ligands is superior to those stabilized by oxygen-containing ligands in catalyzing the Chan-Lam coupling reaction.