Construction Of Bionic Catalytic System With Aerobic Oxidation

In the context of double carbon,greening of chemical reactions is gaining attention.With the widespread use of enzymes,recognized as dedicated and efficient catalysts in living organisms,the establishment of biomimetic catalytic systems that mimic the mechanism of enzyme action has become a research priority for the green chemical industry.Focusing on green chemistry,oxygen,as an air-rich gas,can reduce the energy consumption of the reaction if it is used as the sole oxidant in the oxidation reaction.However,oxygen itself cannot directly oxidize the substrate due to the spin barrier,therefore,the activation of trilinear oxygen is a major difficulty in the aerobic oxidation reaction.In this paper,we focus on the strategy of oxygen activation by transition metal complexes and explore efficient and specific catalytic solutions based on the functionalization of C-H and C-N bonds.This thesis consists of three specific parts of work:（1）Seven different types of ligands were synthesized,and the structure of the complexes was optimized based on quantum chemical calculations.A database of transition metal catalysts for activating oxygen was established for the first time.The optimization and calculation results show that the planar complex is more conducive to the catalytic reaction,and the charge number of the central metal is closely related to the stability of the complex,but this is not the decisive factor to judge the catalytic activity of the ligand.The catalytic activity is also related to the structure-activity relationship of the ligand itself,such as coordination number,space effect,hydrogen bond,etc.This study provides a theoretical basis for the subsequent catalytic oxidation.（2）A transition metal complex（L₆+Mn）-catalyzed aerobic oxidation method was developed using N,N-dimethylaniline demethylation as a model reaction.The results showed that the N-desalkylation could be achieved in the reaction of 5 mol%L₆,5 mol%Mn（OTf）₂,50μL H₂O,oxygen atmosphere,under 460 nm blue light irradiation,in an oil bath at 45℃for 24h.The conversion of the raw material was up to 98%.With the help of UV analysis,electrochemical experiments and LC-MS spiked measurements,the peroxide intermediate species were captured and the system showed good selectivity upon the addition of water.These results reveal that the reaction is a hydrogen transfer reaction caused by single electron transfer.（3）A model reaction for the synthesis ofα,β-unsaturated imines from benzaldehyde and aliphatic amine tetrapyrrole was developed to establish an aerobic oxidation method catalyzed by a transition metal complex（L₂+Fe）.The results show that the direct functionalization ofβ-C-H can be achieved by reacting at 1 mol%L₂,1 mol%Fe（OTf）₂,1 mol%Na₂CO₃,under oxygen atmosphere in an oil bath at 70℃for 24h.The reaction exhibits excellent selectivity.The characteristic peak of L₂ after coordination with Fe（OTf）₂ was captured by NMR titration experiments,based on which the results also demonstrated the successful metallization of the L₂.The results of the controlled experiments indicate that oxygen plays a crucial role in the reaction as the sole oxygen source.Both of the above reactions use oxygen as the only oxidant and successfully break the energy barrier for the activation of oxygen by transition metal complexes.