| Metal organic chemistry is an interdisciplinary discipline formed by the interpenetration of inorganic and organic chemistry and occupies an important position in the field of organic synthesis.Transition metal organic compounds have attracted much attention in the field of green chemistry and organic synthesis due to their good stability,high selectivity,and environmental friendliness.Over the past decades,important progress has been made in the experimental and theoretical applications of single transition metal organocatalytic reactions.Single transition metal catalysts have certain limitations in terms of control of chemoselectivity and atomic utilization,which limit the further improvement of the catalytic performance of metal-organic compounds.In recent years,the design and application of dual transition metal catalytic systems have been rapidly developed,effectively improving the catalytic performance of transition metal catalytic systems.The theoretical study of dual transition metal catalytic systems to reveal the molecular mechanism of their synergistic catalysis,elucidate the key factors to improve the reaction efficiency,and grasp the microscopic nature of controlling the reaction selectivity is of great significance for further improving the performance of catalytic systems and designing new dual transition metal catalytic systems.This thesis investigated the reactions of Cu/Pd and Cu/Ru dual transition metal organic compoundscatalyzed by C-C bond activation and cross-coupling through density functional theory calculations,revealed the microscopic mechanism of the reactions through theoretical calculations,explained the essential reasons for the occurrence of chemoselectivity and stereoselectivity through the analysis of the structures of some key intermediates,and the theoretical models of Cu/Pd and Cu/Ru catalytic cycles were established.1.Four-component boron carbonylation reaction joint catalyzed by Cu/Pd dual transition metals involving vinylarenes,CO,aryl halides,and B2pin2 was investigated.For this reaction,it was found experimentally that β-boryl ketone was the main product when aryl iodide was used as the reaction substrate,while β-boryl vinyl ester was more readily produced when aryl triflates was used as the substrate.We systematically investigated the microscopic mechanism of the reaction,explained the root cause of the chemoselectivity,and clarified the effects of different substrates on the reaction performance.The main findings can be summarized in three aspects as follows:(1)The molecular mechanism of the four-component boron carbonylation reaction was clarified.The reaction involves two catalytic cycles,namely the copper-catalyzed cycle and the palladium-catalyzed cycle;the formation of products mainly undergoes three basic processes,such as the formation of alkyl copper and vinyl alkoxide copper intermediates,the formation of acyl palladium intermediates,and the selective coupling of copper intermediates with palladium intermediates.(2)The essential factors leading to the difference in reactivity for different substrates were clarified.We found that the formation rates of intermediates in copper-catalyzed and palladium-catalyzed cycles were different,and for aryl iodide substrates,the formation of acyl palladium intermediates(12.1 kcal/mol)was easier than that of vinyl alkoxide copper(20.6 kcal/mol),and the coupling reaction of the two intermediates led to the formation of β-boryl ketone;while for aryl triflates,the formation of alkyl copper intermediates(20.6 kcal/mol)is easier than that of the acyl palladium intermediate(21.2 kcal/mol),so the coupling of the alkyl copper intermediate with the acyl palladium intermediate leads to the formation of theβ-boryl vinyl ester product.(3)Revealed that the strength of the C(sp2)-X(X=I,OTf)bond is a key factor controlling the relative stability of the reactive aryl/acyl palladium intermediates.When the substrate is aryl iodide,an energy barrier of 12.1 kcal/mol needs to be overcome to produce the acyl palladium intermediate,while an energy barrier of 21.1 kcal/mol needs to be overcome to form the acyl palladium intermediate when aryl triflates is used as the reaction substrate.This is due to the fact that the bond energy of the C(sp2)-O bond is larger than that of the C(sp2)-I bond,which is 21.4 kcal/mol,while the latter is only 3.5 kcal/mol,so the activation energy barrier of the C(sp2)-O bond is higher,which makes the aryl triflates more difficult to undergo the oxidative addition process,thus causing the difference in reactivity.The theoretical results provide some theoretical guidance to improve the synthesis ofβ-boron carbonyl compounds,and the research results were published in Catalysis Science&Technology.2.The Cu/Ru dual transition metal-catalyzed hydroalkylation reaction of secondary allyl alcohols with ketimine esters for the synthesis of δ-hydroxy esters was investigated.It was found that the racemic allyl alcohol and ketimide ester substrates catalyzed by chiral catalysts could yield(S,R)-type δ-hydroxy ester products with an ee value of 99%.The main results of our theoretical study of this system are as follows:(1)The calculations show that the formation of products goes through four basic processes:Ru-catalyzed dehydrogenation of allyl alcohol intermediates,generation of active copper(Ⅰ)-azomethine,Michael addition reaction,and hydrogenation reduction of ketoesters.(2)We found that the Michael addition process and the hydrogenation reduction process are the key steps controlling the stereoselectivity of the reaction.During Michael addition reaction,β-C is more likely to undergo nucleophilic attack from within the plane of Cu(Ⅰ)-methylenimine yelide intermediate to form the intermediate containing S chiral center;during hydrogenation reduction,K2HPO4 is more likely to undergo hydrogenation outside the plane of hydroxyester intermediate,leading to(S,R)-type δ-hydroxyester product.(3)The relatively strong π-π interaction between the benzene ring and the carbonyl group in the chiral phosphorus ligand of the copper catalyst facilitates the formation of the S configuration of the first chiral center,while the hydrogen bonding interaction between the carbonyl oxygen atom and the hydrogen atom in the Ru catalyst can promote the formation of the R configuration of the second chiral center,which eventually leads to the formation of the(S,R)-type product.The theoretical results reasonably explain the experimental phenomena and provide some theoretical guidance for the synthesis of 1,4-nonadjacent stereocentric compounds.The results of the study have been compiled into a research paper,which is currently in submission status. |
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