Theoretical Study On Mechanism Of Transition-Metal-Catalyzed C-C Bond Formation Reaction Of C=X Compound

Transition-metal-catalyzed carbon-carbon bond formation reaction is central to synthetic organic chemistry.C=X bond ubiquitously exist in organic compounds,and activation and functionalization of these compounds can revolutionize the synthetic strategy of constructing small molecules.Despite significant advances in method development,the mechanistic understandings on transition-meta-catalyzed carbon-carbon bond formation are quite limited.Mechanistic study might provide fundamental insights into the mechanistic investigation.To this end,DFT calculations were carried out in this dissertation to study the mechanism of transition-metal-catalyzed C-C bond formation reaction of C=X compound.The first chapter reviews the methods of transition-metal-catalyzed C-C bond formation of C=X compound,including cross coupling and olefin difunctionalization.Transition-metal-catalyzed C=X compound reactions have been summarized lately,including C=C and C=O compounds functionalization using transition-metal catalysis.In the end,DFT methods and related contents were introduced.The second chapter provides the mechanism of ligand-controlled regioselectivity-switchable copper-catalyzed alkylboration of alkenes.The calculation results reveal that the catalytic cycle mainly proceeds through migratory insertion,oxidative addition and reductive elimination.Meanwhile,the rate-determining step is the oxidative addition of alkyl halides while the regioselectivity-determining step is the migratory insertion of alkenes.Furthermore,the steric hindrances from the substitutes of alkenes,the substitutes on the phosphorus atoms of ligands and Bpin control the regioselectivity.The third chapter conducts a mechanism of Ni(?)-catalyzed oxidative C(sp2)-H/C(sp3)-Hi coupling of benzamides and toluene derivatives,wo previously proposed mechanisms including base-promoted single-electron transfer(SET)and formation of Ni(?)C3F7 intermediate for the generation of iC3F7 radical are found to be disfavored.By contrast,our proposed mechanism involving iodine atom transfer(IAT)between iC3F 7I and the Ni(?)intermediate is kinetically favored.The fourth chapter investigates mechanism of nickel-catalysed suzuki-miyaura coupling of amides.Our study corroborates the previous proposal that the overall catalytic cycle includes three steps:oxidative addition,transmetalation,and reductive elimination.The most feasible transmetalation mechanism involves the ligation of K3PO4 as a Lewis base with the Lewis acid PhBpin.The formed K3PO4-PhBpin readily undergoes the H transfer step with H2O.The calculation results also reveal that the N-Boc substituent group accelerate the oxidative addition via weakening the C-N bond.The last part describes the mechanism and origins of chemo-and regioselectivities of Pd-catalyzed intermolecular ?-bond exchange between benzocyclobutenones and silacyclobutanes.The reaction proceeds via two sequential oxidative additions and two subsequent reductive eliminations.The oxidative addition abilities of the substrates and the trans effect of silyl group synergistically control the chemoselectivity.The regioselectivity of the C-C bond activation of benzocyclobutenone is controlled by the interaction between substrate and palladium.