Substituted Arylboronic Acid Synthesis

A variety of substituted arylboronic acids are important intermediates of organic synthesis, intermediates of medicines and pesticides. They play an important role in the preparation of bio-actie reagents or materials research, and have been widely used in C-C, C-O, C-N bond formation. In this article, the synthesis of fluoro-substituted phenylboronic acid,p-bromophenylboronic acid and multiarylboronic acid and their process improvement were studied in detail.P-fluorophenylboronic acid was prepared according to Griganrd reagent. The influencing factors on yield were analyzed with the orthogonal experiment, the reactant molar ratio was greatest, followed by the reaction temperature, and optimized process was obtained:the reactant molar ratio of p-fluorobromobenzene to trimethyl borate was 1:2, the nucleophilic substitution temperature was-20℃, and the reaction time was 2 h, the overall product yield was 60%. In addition, the synthesis of m-fluorophenylboronic acid and o-fluorophenylboronic acid were also studied.In the synthesis of p-bromophenylboronic acid, to change traditional synthetic route of 1,4-Dibromobenzene as raw materials, using p-Bromoiodobenzene as substrate, by exchange reaction of iodine-magnesium with isopropyl magnesium bromide, followed by the nucleophilic substitution reactions of p-bromophenylboronic acid. An optimized process was obtained by investigating the influence of factors on yield of p-bromophenylboronic acid:the reactant molar ratio of isopropyl magnesium bromide to p-Bromoiodobenzene was 2:1, the exchange temperature was-10℃, the reactant molar ratio of the trimethyl borate to p-Bromoiodobenzene was 3:1, the nucleophilic substitution temperature was-40℃, and the reaction time was 2 h, the total yield of 69.8%. A series of multiarylboronic acid,β-naphthaleneboronic acid represented, were prepared by Grignard reagent, and an optimized process was obtained by investigating the influence of boride reagent, raw material ratio, reaction temperature and reaction time on yield ofβ-naphthaleneboronic acid:the reactant molar ratio ofβ-Bromonaphthalene to the trimethyl borate was 1:2, the nucleophilic substitution temperature was-20-22℃, the reaction time was 3 h, the total yield was 80.7%.All products were characterized by IR, 1HNMR, and results were in accord with target produncts.