DFT Study On The Mechanisms Of Several Amination Reactions Catalyzed By Gold And Copper

Nitrogen-containing compounds are ubiquitous in natural products and artificial pharmaceuticals, a majority of compounds with pharmaceutical and biological activities contain one nitrogen functional group at least. In recent years, investigation of transition metal catalyzed unsaturated C-C bonds functionalization has attracted a great amount of research groups’ interest. Acting as one of the essential research tools,computation chemistry provides great convenience to investigations of alkenes and alkynes functionalization reactions, for example, computation chemistry has an advantage of simulating the structures of intermediates and transition states and speculating the mechanism of the reactions. In this thesis, we put most of our focus on mechanism study into two kinds of novel transition metal catalyzed functionalization reactions of alkenes and alkynes employing quantum chemistry theory and Gaussian09 software. The main results are summarized as follows:The mechanism of Au Cl(PPh)3 catalyzed aminoarlylation of NFSI and alkynes were investigated at B3LYP/6-31G*//B3LYP/6-31+G** level of theory, obtained four pathways. The reaction can be classified into four steps: oxidative addition, alkyne insertion, hydrogen abstraction and reductive elimination. In the first step, the gold was initially oxidated from monovalence to trivalence with the highest energy barrier,which meant the rate-determining step. Then following step was the alkyne’s insertion into Au-N bond, which could generate the Au-F bond. The third step was the“hydrogen abstraction” step leading to the aminoarylation of alkynes. The seven-membered ring with a relatively bulkier ring-tension could spontaneously trigger a reductive elimination step with the generation of the desired product.Considering about the steric hindrance, the insertion site of Au-N bond is superior to that of Au-F bond. Comparing with the thermodynamic data of hydrogen abstraction step, Au-F bond H-abstraction with lower energy is more favorable.We also investigated the mechanism of a novel radical aminofluorination of styrenes using density functional theory under B3LYP/6-31+G** level of theory.Employing copper(I) as the transition metal catalyst, the radical aminofluorination of styrenes with NFSI was realized with high regio-selectivity. In order to make clear the mechanism of this novel reaction, we made a detailed DFT study to investigate the issues, including the origin of nitrogen radical and the role of NFSI. Thecomputational study revealed that the NFSI was utilized as both nitrogen source and radical fluorine source, thus extending the use of this reagent in organic synthesis field.