Mechanistic Study On Palladium-Catalyzed Asymmetric Synthesis Of Allylic Amines From Vinyl Cyclic Carbonates

Chiral allylic amines are fundamental building blocks in organic synthesis,and their preparation is of high synthetic and industrial interest.In 2016,Kleij and co-workers developed the first asymmetric synthesis of α,α-disubstituted allylic N-arylamines based on a palladium-catalyzed allylic amination.The protocol used highly modular vinyl cyclic carbonates and unactivated aromatic amine nucleophiles as substrates.The catalytic process featured minimal waste production,ample scope in reaction partners,high asymmetric induction up to 97% ee,and operational simplicity.However,the reaction mechanism of this reaction is not yet clear.In this thesis,the detailed mechanism was investigated by density functional theory(DFT)calculations.The computations show that the overall catalytic cycle consists of four major steps: C-O bond oxidative addition,CO2 release,proton migration and nucleophilic attack.First,the Pd catalyst attacks the C-O bond,and then undergoes a six-membered ring transition state to release CO2,forming a six-membered ring containing a Pd-O bond.The proton transforms from aniline to oxygen atom while the Pd-O bond broken and six-membered ring opened.Finally,the nitrogen atom nucleophilically attacks the tertiary allyl carbon atom to generate(S)product.The calculated results are in agreement with the experiment results.Three key questions were explained:(1)the racemic substrate yields a single configuration product because the intermediates which after CO2 release can be interconverted with each other easily;(2)the selectivity of the product is arised from the proton migration process;(3)due to the high energy of the nucleophilic attack on carbon atoms by nitrogen atoms,the linear product was thus not observed.The present results will have important implications for a better understanding of the relevant reactions.