Theoretical Studies About Cyclization Reactions Synthesis Of Pyrrole Derivatives Catalyzed By Palladium Or Nickel

The development of the chemical industry is inseparable from highly efficient and economical catalysts.Transition metal catalysts are widely used in chemical reactions to improve the efficiency,selectivity and stability of reaction process.Cyclization reaction to construct heterocyclic compounds catalyzed by transition metal is one of the important fields of metal-organic chemistry.In recent years,with the in-depth development and utilization of catalysts,reactions to construct heterocyclic compounds have developed rapidly.Significant progress has been made in terms of substrate reaction range,reaction yield,and selectivity.In this paper,the mechanisms of pyrrole derivatives formation from the cyclization reaction of alkyne and nitrogen-containing substrates catalyzed by transition metal palladium and nickel are explored in detail.After obtaining the corresponding potential energy profiles,additional theoretical studies were carried out to explore the influence of other reaction conditions,which would provide a theoretical basis for the improvement of subsequent experimental studies.The whole dissertation is divided into four chapters.In Chapter 1,the research progress in the synthesis of five-membered carbo-and hetero-cycles compounds with different reaction substrates catalyzed by transition metals is briefly reviewed.In Chapter 2,the relevant theories and computational methods are briefly introduced.In Chapters 3 and 4,detailed theoretical studies of palladium-and nickel-catalyzed cyclization reactions involving alkynes and different nitrogen-containing substrates are carried out,respectively.The main computational contents are as follows:1.The mechanisms of Palladium-catalyzed reaction of alkynes and tert-butyl isocyanide to form pyrroles.Density Functional Theory was carried out to study the mechanisms of Pd-catalyzed reaction of alkynes and tert-butyl isocyanide forming pyrroles in detail.In the case of di-palladium catalysis,the calculation results indicated that alkyne insertion,isocyanide insertion,intramolecular cyclization,isocyanide insertion,isomerization and ligand substitution were involved in the mechanism.The above mechanism was explored when terminal alkyne was used as a model reactant.The intramolecular cyclization process was calculated to be the rate-determining step in the catalytic cycle.The substituent effects on the regioselectivity of reaction were also analyzed.In addition,detailed calculations on mono-palladium catalysis showed that the activity of mononuclear catalysis was not as high as that of di-palladium catalysis.2.The mechanisms of Nickel-catalyzed reaction of diynes and methylenesaziridines to form pyrroles.Density Functional Theory was carried out to study the mechanisms of Ni-catalyzed reaction of diynes and methylene aziridines forming pyrroles in detail.1,6-diyne and1-benzyl-2-methyleneaziridine were used as model reactants.Having ruled out the mechanisms containing β-carbon elimination and α-carbon elimination,the calculation results indicated that the preferred catalytic cycle is a mix mechanism of the cod dissociative and cod associative,which is comprised with ligand substitution of cod with methyleneaziridine,oxidative addition,ligand substitution of diyne with cod,alkyne insertion,reductive elimination.Throughout the catalytic cycle of diynes,the oxidative addition process was calculated to be the rate-determining step in the catalytic cycle.Each of alkyne units of diyne have important roles.One acts as the reactant and inserts into the Ni-C bond to form the cycle expansion complex;the other free alkyne unit makes an effect as a ligand coordinated to Nickel to promote the oxidative addition step.