Theoretical Study Of Catellani-Lautens-like Reactions Catalyzed By Pd(Ⅱ)

In this thesis,we used density functional theory calculations to carriy out the mechanistic studies of two catatylic systems.The detailed reaction natures and mechanisms for the two systems were described,explored and explained with the aid of the DFT calculations.The various influences such as additives,ligands and solvents on the reactions studied in this thesis were also probed.This work would provide further understanding of the reactions and possible theoretical guidance.Specific works are as follows:(1)We use the density functional theory to study the kinetics of metal iodide-catalyzed aromatic iodination acylation / alkenylation reaction mechanism based on the Catellani-Lautens reactions,the Pd-catalyzed cross-coupling of aryl iodide,benzoic anhydride and ethyl acrylate provided a useful alternative to synthesize alkenylated aryl ketones with good selectivity and functional-group tolerance.In this manuscript,density functional theory(DFT)calculations were performed to address the detailed reaction mechanism.Computational results support the experimentally proposed Pd(0)-Pd(Ⅱ)-Pd(Ⅳ)catalytic cycle and further clarify that the rate-determining step is the oxidative addition of benzoic anhydride,the regioselectivity-determining step is the migratory insertion of ethyl acrylate and the following β-H elimination determines the stereoselectivity.The regioselectivity can be attributed to the steric and electronic effect of ethyl acrylate and the stereoselectivity can be explained by the steric repulsion between the toluene moiety and the CO2 Et moiety.Furthermore,we found that norbornene not only acts as the removable scaffold in Catellani-Lautens-type reactions,but also plays the role of suppressing the competitive migratory insertion of ethyl acetate.Norbornene insertion and ethyl acetate insertion are found to have close free energy barriers,which shed light on the origin of using stoichiometric amounts of norbornene.(2)The theoretical study of the second project is also based on the Catellani-Lautens reactions.We carried out a detailed mechanistic study on the carbon-carbon bond formation through the reaction of a Pd(Ⅱ)complex with 1-tosylaziridine,with the aid of density functional theory calculations.In our theoretical study,four possible paths were proposed and all of them were examined.The experimental results indicated that Pd(Ⅳ)is not involved in the reaction.Our theoretical investigation shows that the mechanism involving the oxidation addition step that affords a Pd(Ⅳ)center is not feasible,while the Pd(Ⅱ)center is kept via a SN2 mechanism.Additionally,the mechanism involving a σ-bond metathesis was also computationally examined and found that this path is not achievable.This theorectical study is done in coorperation with the experimentalists who carried out the experimental work.