Theoretical Studies Of C?H Amination Reactions Catalyzed By Iridium Complexes

Transition-metal-catalyzed C–H bond amination for installing C–N functionality has become a vital method in organic synthetic transformations.Development of efficient and convenient method for C-H amination reactions with controlling selectivity is of great interest and importance.An understanding of the exact reaction mechanism and origins of selectivity is an essential aspect for developing desired reactions.However,It is hard to conduct mechanistic studies at the molecular and electronic levels though traditional experimental methods.In this thesis,iridium complexes catalyzed C?H aminations have been computationally studied based on density functional theory.Cp*Ir（III）-catalyzed allylic C–H amination reaction of 1-decene with methyl dioxazolone has been investigated by DFT calculations.The computational results show that Ag NTf₂ plays an important role in the formation of active species[Cp*Ir（OAc）]⁺and suggest that the reaction mainly involves the following steps:alkene coordination,allylic C（sp³）–H activation,decarboxylation,migratory insertion,and the final protonation.The allylic C–H activation is calculated to be the rate-determining step.The regioselectivity of the reaction is due to the lack of electrons in the allyl carbon atom of the key Ir（V）-nitrenoid species and the earlier transition state.By comparison of Cp*Ir（III）-and Cp*Co（III）-catalyzed processes,we know that the high catalytic activity for Ir catalyst is mainly attributed to the relative stable of alkene-coordinatingπ-complex and the stronger metal?H interaction assisting hydrogen transfer in comparison with Co system.The C（sp²）?H amination of aryl group catalyzed by a Cp*Ir（III）complex has been computationally studied.Theoretical studies show that the active species of the reaction is cationic active species[Cp*Ir（Opiv）]⁺.The reaction mechanism involves sequential C（sp²）–H activation,coordination of azide compounds,nitrene formation,nitrene insertion,and final protonation.The rate-determining step of the reaction is the formation of nitrenoid species.Cp*Rh（III）-catalyzed formation of nitrenoid species is unfavorable both thermodynamically and kinetically,resulting in no catalytic activity.The geometrical structure analysis showed that it is an earlier transition state of metal nitrenoid species formation in Cp*Ir（III）catalysis.EDA-NOCV analysis showed a stronger orbital interaction between metal Ir and N atom in the transition state of metal nitrenoid species formation.The theoretical study of Cp*Ir（III）-catalyzed stepwise polymerization of C–H amination shows that the active species is cationic active species with the coordination of monocarboxylic for chain initiation,chain growth and chain termination.These reactions involve sequential coordination of amide substrate,aryl C（sp²）–H activation,nitrene formation,nitrene insertion,and final protonation.However,the rate-determining step of chain initiation is C–H activation,and the rate-determining step of chain growth is the formation of nitrene.Chain initiation and chain growth compete with two possible chain termination mechanisms,respectively.The combination of different substrates may regulate the electronic factors and steric hindrance factors,thus influencing the competition of chain termination,and obtaining C–H amination stepwise polymerization products with different polymerization degrees.