Study On The Coupling Reaction Of Chlorinated Aromatic Heterocycles Catalyzed By Novel N-heterocyclic Carbene Palladium

The Suzuki-Miyaura and Buchwald-Hartwig coupling reactions catalyzed by palladium complexes play an important role in the synthesis of Pharmaceutical intermediate,pesticides,organic optoelectronic materials and other organic functional materials.In recent years,the nitrogen heterocyclic carbene palladium complex(NHC-Pd)has become a research hotspot due to its advantages of green environmental protection and high efficiency.This paper aims to study the synthesis of a new class of NHC-Pd complexes to catalyze hetero(aryl)ring-heterocyclic coupling substrates.Five novel nitrogen heterocyclic skeleton carbene complexes C1,C2,C3,Cs1 and Cs2 were designed and synthesized,and their structures were characterized by nuclear magnetic resonance and X-ray.Through the screening of five novel nitrogen heterocyclic skeleton carbene palladium complexes,Studying these complexes as precatalysts tocatalyze the coupling reaction between a chlorinated aromatic heterocycle and a heteroaromatic ring,The substrate type was expanded under the optimal catalytic system to obtain a series of heterocyclic coupling products.Improving the catalytic performance of the catalyst by changing the nitrogen heterocyclic carbene imidazole ring skeleton,The results show that the steric hindrance effect of the skeleton substituent can improve the stability of the catalyst;The bridgehead carbon can effectively prevent the aromatic amine from turning around the carbon-nitrogen bond.Prevent ?-hydrogen elimination and catalyst deactivationThe study found that:(1)the nitrogen heterocyclic carbene imidazole ring skeleton ring protects the metal palladium center,And the introduction of isopropyl group can greatly improve the efficiency of the catalyst;(2)The two t-butyl groups introduced on the fluorenyl skeleton enhance the electron cloud density and promote the oxidative addition reaction,thereby facilitating the catalytic cycle.(3)Under the optimal catalytic system,the two active ligands of C1 and Cs1 are used as catalysts to expand the substrate of chloroheterocyclic(aromatic)ring-heterocyclic coupling reaction,Some of these coupled products are well suited for use in pharmaceutical intermediates and optoelectronic materials.