Research And Application Of Polyhalo Genated Aromatic Hydrocarbon C-O Coupling Reaction

In recent years,the copper-catalyzed Ullmann coupling reaction is a crucial tool for the formation of C-C and C-X（X=O,S,N,etc.）bonds in organic synthesis and has diverse applications in fields such as industry,agriculture,pharmaceuticals,and mate-rials.The reactivity sequence for aryl halogenated hydrocarbons in transition metal-cat-alyzed C-O bond coupling reactions is ArI>ArBr>ArCl,and under alkaline condi-tions,the greater electronegativity of the leaving group results in an S_N2 reaction with the sequence of reactivity being ArF>>ArCl>ArBr>ArI.For polyhalogenated ben-zene substrates,some reactions selectively undergo substitution reactions,while others undergo coupling reactions under the Cu catalytic system,and the key factors affecting selectivity have not been fully elucidated.Although bidentate ligand oxalyldiamine de-rivatives have been reported to effectively promote the C-O bond coupling reaction of aryl chloride,it remains unclear whether the specific electron donor effect of the ligand or its structural factors play a key role in the Ullmann coupling reaction.This thesis aims to establish the synergistic effect between the oxaldiamine struc-ture and the coupling reaction and reveal the relationship between them,based on the results obtained using polyhalogenated benzene as a substrate.Theoretical and experi-mental approaches were used to determine the key factors affecting chemical selectivity（substitution reaction or coupling reaction）and to develop highly active and selective copper catalysts.The paper is divided into three parts.First,the selectivity of the coupling reaction between polyhalogenated benzene and alcohol was studied,and it was found that the coordination ability of the ligand plays a crucial role in determining the selectivity of the reaction.Under strong alkali conditions,the product of the coupling reaction is dominated by the ligand,whereas weak alkalinity is dominated by the coupling reactionSecond,the influence of the ligand structure on the reaction was investigated by studying the conjugation effect of the ligand.It was found that the activity of the cata-lyst could be increased by enhancing the coordination ability of the oxaldiamine ligand and copper.The coordination ability of oxaldiamine derivatives with copper could also be increased by incorporating electron-donor substituents（-CH₃,-OCH₃）on the ligand.Based on these findings,we designed a ligand that was able to verify our expectations.Finally,the synthesis of diphenyl ethers and their derivatives was studied using chlorobenzene（solvent-free）and polyhalogenated bromobenzene（solvent DMSO）as substrates and phenol at different temperatures in the coupling of C-O.It was found that the[Cu]/L20 system had higher catalytic efficiency than other[Cu]/ligand catalytic systems.These results provide valuable insights into the development of highly active and selective copper catalysts and the factors affecting selectivity in the Ullmann cou-pling reaction.