Theoretical Studies On Ni-catalyzed C-C Bond Activation Of Benzocyclobutenones And Ag₂O Synthesis Of Pyrazoles From Nitroalkenes And Trifluorodiazoethanes

In recent years,the cyclization of unsaturated compounds catalyzed by transition metal complexes and transition metal oxides has been extensively developed and applied.Although experimentally reported transition metal complexes catalyzed benzocyclobutenes?BCBs?and 1,3-dienes compounds to synthesize eight-membered ring compounds,and transition metal oxides catalyzed nitroolefinsand trifluorodiazoethane Five-membered heterocyclic compounds containing nitrogen were synthesized,but the theoretical details of these reactions are still lacking.In this paper,we systematically studied the mechanism of catalytic activation of C-C bonds,C-H and N-H bonds by transition metals Ni and Ag using density functional theory?DFT?.Through our research,we hope to make a comprehensive understanding and judgment of the influencing factors of the transition metal catalyzed reaction mechanism,so as to provide theoretical guidance for the selection of the catalyst and the modification of the substrate in the subsequent experiments.In chapter 3 of this paper,we systematically studied a strategy that recently developed by Martin and co-workers for Ni?0?-complex-catalyzed[4+4]annulation of primary benzocyclobutenones?BCBs?and 1,3-dienes.Use density functional theory?DFT?studies to elucidate the catalytic mechanism.A density functional theory study was performed to clarify the catalytic mechanism.The results provide insights into the origins of the chemo-,regio-,and diastereoselectivity.The calculation results explain why only P?C₆H₅CF₃?₃,among several candidates,performed well and why the[4+4]annulation of BCB with a 1,3-diene was achieved with a Ni?0?but not with a Rh?I?catalyst.In the fourth chapter of this paper,we use density functional theory?DFT?to theoretically study the mechanism of Ag₂O-catalyzed 1,3-dipolar cycloaddition of nitro-alkene and trifluorodiazoethane by Ag₂O developed by Ma and co-workers.The calculation results confirm that when Ag₂O is used as a catalyst,the reaction mechanism for synthesizing five-membered heterocyclic pyrazole compounds is superior to that without Ag₂O-catalyzed reaction mechanism.Through the distorted/interaction model and electrostatic potential?ESP?analysis,it was found that the interaction energy and the electrical site of the ringing position play a key role in regioselectivity.In addition,the frontier molecular orbital theory was used to further analyze the HOMO and LUMO orbital transitions of CF₃CHN₂ and[CF₃CN₂]Ag,respectively,when the substrates for the reaction were all nitroolefins.We found that the transition energy gap between nitroolefins and CF₃CHN₂ is higher than that between nitroolefins and[CF₃CN₂]Ag,which explains why it shows high reactivity under Ag₂O catalyst.Therefore,it also shows that under the catalysis of metal Ag,the synthesis of five-membered heterocycles will be easier.