Theoretical Study On Selective Catalytic Amidation Of Allyl C-H With Rhodium And Iridium Complexes

Due to the ubiquity of nitrogen-containing functionalities in both natural and synthetic bioactive molecules,many synthetic chemists have focused on the exploration of amination reactions under mild conditions.The traditional strategy for constructing C-N bonds is to preinstall the directing groups.The most typical example is palladium-catalyzed Buchwald-Hartwig amination reaction.However,this synthetic application requires pre-activation of the directing groups,and its subsequent removal step is also an issue to be considered.Transition metal catalyzed C-H bond functionalization has provided a straightforward way to construct C-N bonds,which offers higher atomic economy.In homogeneous catalysis,allyl,an important synthon in organic synthesis,is easy to accept nucleophilic attack as an active "actor" ligand.In this paper,we studied the selective catalytic amidation of allyl C-H with Rhodium and Iridium complexes from the perspective of theoretical computation.The results will be helpful to improve the performances of existing catalysts or develop new catalysts,which is significant for the development of olefin C-H amidation.First,we carried out a theoretical study on the selective catalytic C-H amination of allyl by Cp*Rh(Ⅲ)or Cp*Ir(Ⅲ)catalysts using DFT calculations.The key steps affecting the branch selectivity and the origin of regioselectivity were thoroughly studied.The calculation results showed that the C-H activation of the terminal alkene is rate-determining in whole reaction free energy profile,and the subsequent C-N bond coupling is the step that determining the regioselectivity.Distortion-interaction model,energy decomposition analysis(EDA)model and natural bond orbital(NBO)charges indicate that the reason of the branched selectivity is the Coulomb i in C-N bond forming step.Next,a theoretical study of the trans-1,2-disubstituted olefin C-H amination by CpXIr(Ⅲ)catalysts was carried out using DFT theory.The selective C-H activation of olefin first results allyl intermediate,which then undergoes selective C-H amination.Different CpX ligands were selected as the computational models.The reaction mechanisms of allyl C-H activation and amination were studied systematically.Key steps affecting allyl α-C/β-C amination and the reasons of β/αamination selectivity have been quantitatively analyzed.The results showed that the polarization effect in the C-N bond step is the key factor affecting the regioselectivity of C-H amination catalyzed by CpXIr(Ⅲ)complex.