Computational Study On Difunctionalization Reactions Of Terminal Olefin Catalyzed By Nickel-Based Catalysts Activating

In the past few decades,unactivated olefin functionalization catalyzed by transition metal catalysts has been used to synthesize many valuablechemical compounds and materials.Ni-catalyzed dicarbofunctionalization of alkenes represents one of the most efficient strategies to install two vicinal chemical bonds and thus build molecular complexity from simple and readily available feedstock chemicals.Controlling the reaction sequence of two different carbon sources and the selectivity of different reaction sites is the key to the success of this reaction.However,due to the lability of organonickel species and the multiple mechanistic manifolds,determination of the detailed mechanisms remains challenging in most cases,which severely restricts further development of new reagents,new reactions,new concepts and new strategies.This project intends to conduct a systematic study on the redox neutral and reductive dicarbofunctionalization of alkenes.The interplay of steric,electrostatic,and orbital interaction effects revealed by DFT calculations on how to impact the reaction mechanism and substrate-dependent selectivity can offer the in-depth insight for further developments of regiodivergent functionalization strategies of simple alkenes.In this thesis,on basis of recently reported experimental work of unactivated olefin functionalization reactions,The reaction mechanism and regioselectivity of olefin functionalization reactions have been systematically studied using Density Functional Theory.In terms of natural bond orbit analysis(NBO),buried volume ratio(V_bur%),and energy decomposition method(EDA)are used to activate C=C double bonds by nickel complexes,the main conclusions are summarized as follows:(1)Computational results demonstrate that these reactions are generally composed of several steps including oxidative addition,carbonickelation,H-shift/transmetalation and reductive elimination.Among these steps,the key one responsible for the regioselectivity depends upon the organic halides utilized.(2)For nickel-catalyzed the difunctionalization of aminopyrimidine olefins,among these steps,the key one responsible for the regioselectivity depends upon the organic halides utilized.Natural bond orbital(NBO)analysis,energy decomposition analysis(EDA)and buried volume calculation indicate that steric effect is a common contributor of the regioselectivity,while other energy terms,such as electrostatic interaction,have significant and even dominant effects on the specific regioselectivity 1,3-diarylation reaction.Furthermore,the key reason of successfully suppressing Heck and/or Suzuki products lies in that the formation of Heck and/or Suzuki products is thermodynamically less favourable.Comparison of total reaction barriers of rate-limiting step(combined transmetalation and reductive elimination processes)demonstrates that the electron-induced effect of various organic halides significantly causes the different bonding ability between Ni atom and allyl moiety.As a result,transmetalation and reductive elimination processes made distinct contribution to reducing the total activation free energy of rate-limiting step of various difunctionalized reactions.(3)For the substrate of aromatic vinyl reaction systems,the single electron transfer process is the rate-determining step of olefin functionalization reactions mediated by nickel catalyst.Moreover,the directional ligand of nickel complexes plays an important role in the homogetic cleavage of C-I bonds,which significantly stabilizes the corresponding transition states...