Theoretical And Computational Studies Of Reactions Catalyzed By Palladium-Organic Coordination Cages And Transition Metals

Theoretical and computational chemistry are critical disciplines in modern chemical research,which aim to investigate the characteristics of molecules,the mechanisms of chemical reactions,and forecast new chemical reactions through computer simulations and theoretical models.This thesis begins with an introduction to computational chemistry in Chapter 1,followed by a series of detailed studies in subsequent chapters.Chapter 2 focuses on exploring the efficient catalysis and regioselectivity of the Diels-Alder reaction using supramolecular metal cages.Chapter 3 examines the enantioselective hydrosilylation of 1,1-disubstituted linkages catalyzed by transition metal nickel.Chapter 4 presents a study on the reaction mechanism and selectivity of transition metal palladium-catalyzed ligand-controlled selective lactonization of binary carboxylic acids.Finally,Chapter 5 summarizes the findings of the thesis and provides an outlook for future research.Ⅰ.Supramolecular metal-organic cage catalysis has emerged as a rapidly developing research area in recent years.However,the theoretical understanding of the reaction mechanism,reaction activity,and selectivity control factors of supramolecular catalysis is still lacking.The cover chapter of this thesis aims to investigate the mechanism,catalytic efficiency,and regioselectivity of the Diels-Alder reaction in bulk solution and in two[Pd₆L₄]¹²⁺supramolecular cages using density functional theory.Our computational results agree well with experimental findings.The catalytic efficiency of the bowl-shaped cage C1is attributed to the favorable host-guest stability of the transition state and entropic effects.The shift in regioselectivity from 9,10-to 1,4-addition within octahedral cage C2 is attributed to confinement effects and non-covalent interactions.This study contributes to a better understanding of[Pd₆L₄]¹²⁺metal-catalyzed reactions and provides a detailed mechanistic profile that is difficult to obtain from experiments.The findings will aid in the development of more efficient and selective supramolecular catalysis.Ⅱ.Transition metal-catalyzed asymmetric hydrosilylation of unsaturated bonds,particularly olefins and alkynes,is a highly efficient and straightforward method for constructing various chiral organosilanes.Such intermediates have applications in organic synthesis,materials science,and drug discovery due to their multiple reactivity,stability,and low toxicity.This chapter presents the first example of Ni-catalyzed asymmetric hydrosilylation reactions of 1,1-disubstituted alleles,which exhibit high levels of regioselectivity and enantioselectivity.The key to achieving such stereoselective hydrosilylation reactions is the development of bisphosphite ligands（SPSi PO）derived from SPSi OL.The reaction mechanism and enantioselectivity were elucidated through DFT calculations,where the rate determination step was found to correspond well with the experimental kinetic isotope effect.Our computational results showed that the C-H-πinteraction,H-H repulsion,and H-bonding between the substrate and ligand are the critical factors that affect the reaction selectivity.Ⅲ.The search for more efficient and highly selective C-H bonded oxidation of hydrocarbons and biomolecules is a challenging research topic.Understanding the mechanisms and controlling factors of C-H oxidation reactions can broaden the scope of these synthetic reactions and lead to the discovery of new,more efficient,environmentally friendly,and practical C-H oxidation reactions.In this chapter,we investigate the Pd（II）-catalyzed quinoline-pyridone ligand-controlled lactonization of dicarboxylic acids and reveal that the formation of C-O bonds proceeds through a proton-coupled anti-oxypalladation mechanism,which is the rate determination step.We found that the two carboxyl groups of the dicarboxylic acid play different roles:one cooperates with the metal Pd center to assist in the activation of the C-H bond,and the other completes the construction of the lactonized C-O bond.Specifically,the five-membered chelating ligand leads toβ-C-H bond activation andδ-lactonization products,while the six-membered chelating ligand leads toγ-lactonization products.The chelation angle and flexibility of the ligand play a crucial role in the selectivity of the product.