Synthesis And Coupling Applications Of Phenyl Diboronic Acids

Various substituted arylboronic acids are important intermediates of medicines, pesticides and organic synthesis. They have been widely used in C-C, C-O, C-N bond formation, and play an important role in the preparation of bio-actie reagents or new materials research. In this thesis, the synthesis of1,4-benzenediboronic acid and4,4’-biphenyldiboronic acid and their process improvement were studied in detail. Meanwhile, under the catalysis of nickel complexes, the coupling activity and reaction rule of this two phenyl diboronic acids coupling with halogenated aromatics were investigated as well.1,4-benzenediboronic acid was first prepared according to Grignard reagent method, and the optimized process was obtained by investigating the influence of boride reagent, raw material ratio, reaction temperature and reaction time on yield of1,4-benzenediboronic acid, which the reactant molar ratio of dibromobenzene to the tributyl borate was1:3, the nucleophilie substitution temperature was-40℃, and the reaction time was5h. After column chromatography purification, the the yield was54.4%. Using dibromobenzene and tributyl borate as raw material, the "one-pot" method was studied to synthesize1,4-benzenediboronic acid. An optimized process was obtained by investigating the influence of boride reagent, raw material ratio and solvent on the yield of1,4-benzenediboronic acid, which the reactant molar ratio of dibromobenzene to the tributyl borate was1:2.5,30℃response4hours, and the yield was49.6%after purification. After comprehensive comparison and analysis, the "one pot" method is more suitable for the synthesis of1,4-benzenediboronic acid.4,4’-Biphenyldiboronic acid was synthesized through "one-pot" and N-butyl lithium method, respectively. An optimized process of "one-pot" was obtained by investigating the influence of boride reagent, reaction temperature, reaction time, raw material ratio and solvent on the yield of4,4’-biphenyldiboronic acid, which the reactant molar ratio of dibromobiphenyl to the tributyl borate was1:2.5,50℃response6hours, and the yield was48.3%after purification. The yield can reach56.8%by n-butyl lithium method. Because of the valuableness and instability of n-butyl lithium, the "one-pot" method is a appropriate method to synthesis4,4’-Biphenyldiboronic acid.With the catalysis of Ni(PPh3)2Cl2, the Suzuki coupling reaction happened successfully between dibromobenzene and1,4-benzenediboronic acid or4,4’-biphenyldiboronic acid. Both obtained the linear phenylene polymers with high degree of polymerization and the terminal groups were boric acid or bromine. These two kinds of products had a similar structure, but1,4-benzenediboronic acid had a higher reactivity and the average molecular weight of the obtained polymers were larger. With the catalysis of nickel complexes,1,4-benzenediboronic acid can also react with4-bromine toluene or4-chlorine toluene. Both the products were p-methyl terphenyls and4’-methyl-4-diphenyl boric acid. The reaction activity of4-bromine toluene was little better than4-chlorine toluene. It is shown that the nickel catalyst could effectively catalyze chlorinated aromatics cross-coupling with benzenediboronic acid.