Study On Mechanism Of Ullmann C-O, C-N Coupling Reactions Material Science

In this thesis, the Density functional theory was used to study two typical Ullmann reactions which were catalyzed by copper salt. One was the CuI-catalyzed C-O coupling reaction in aryl bromide-alkenyl triflates molecule. The other was the CuI-catalyzed C-N cross-coupling reaction between Halogenated benzene and a-amino acids. The purposes of these researches were to design reasonable microreaction steps, to verify and optimize the configurations and relative parameters of reactants, intermediates, transition states and products in C-O, C-N Ullman coupling reaction, to get reliable thermodynamic and kinetic data, thus prove the catalytic principle of copper source. On this basis, the impacts of changes in the catalyst ligands on the catalytic performance in such reactions were discussed. These might provide some theoretical support for experimental researchers looking for better catalyst. In addition, comparative experiments with different amino acids were operated to clear the amino acids’character in Ullman reaction in micro level. This could provide theoretical evidence for amino acids’ action principle which was predicted by experimental researchers in the reaction, and point the direction of looking for better ligands.The conclusions obtained according to the work are as follows.(1)The mechanism of CuI-catalyzed C-O coupling reaction in aryl bromide-alkenyl triflates molecule was analyzed. The mechanism and energy change of the same reaction without catalyst was also studied, the result implied that the activation energy of the Cul-catalyzed C-O coupling reaction in aryl bromide-alkenyl triflates molecule is lower than that without catalyst, which proved the benefit of Cul to this reaction.(2)The mechanism of CuI-catalyzed C-N cross-coupling reaction between Halogenated benzene and a-amino acids was studied. A catalysis cycle was designed, and was proved reasonable by optimized computation. The Cul catalyst lowered the activation energy of the C-N cross-coupling reaction between Halogenated benzene and a-amino acids. The result showed Cul combined to amino acids at the beginning of the reaction. As the ligand, amino acids also promoted the reaction. Cul showed good selectivity, lowered the activation energy of the reaction, and catalyzed the cross-coupling reaction between halogenated aromatic contents and acid amides. The calculation result matched the experiment result, which proved the copper source catalysts’assistance to this kind of reaction. In addition, the configuration parameters, energies and charge densities of the compounds in the reaction were analyzed. The mechanism of catalysis was clarified in theory.(3)The C-N cross-coupling reactions between Halogenated benzene and a-amino acids were catalyzed by Cul, CuCl and CuBr respectively. The reaction processes and relative energies of the three reactions were compared. The result indicated that different ligands do change some configuration parameters, charge densities and energies but not steps of these reactions and the basic configurations of compounds. The changes in bond lengths, energies and charge densities of relative configurations of the three reactions were compared. The activation energy of reactions catalyzed by CuCl is the lowest. This implies CuCl has better catalytic effect.(4) The mechanism of reactions which were operated with Phenylalanine and L-Valine was studied. The result showed no change in reaction process and rate-controlling steps. But L-Valine was combined to CuI easier. In subsequent steps, the activation energies of rate-controlling steps in the reaction with L-Valine were lower than those in the reaction with Phenylalanine. It indicated that the reaction with L-Valine was more easily to carry out, and had better productive rate which matched experiment results. The microscopic processes of the two different amino acids involved reactions were analyzed and compared. It was confirmed that the amino acids was not only as nucleophile, but also ligands which could combined with copper catalyst into catalytic system to improve catalytic capability.