Improvement on Synthesis of Different Alkyl-Phenylboronic Acid

Various alkyl-phenylboronic acids have been widely used in the fields of electronics, chemistry, medicine and biology, especially in glucose sensors and intermediates of medicines. In this paper, the syntheses of two or three different alkyl-phenylboronic acids and the improvement on synthesis processes were studied with Grignard reagent method in detail. The influencing factors such as temperature, reaction time, reactant molar ratio were analyzed with the orthogonal experiment; optimized processes for the preparation of different alkyl-phenylboronic acids were thus obtained using different alkylborates as original materials. Based on the analysis of the experiment results, a "one-pot" method was proposed and checked to synthesize several different alkyl-phenylboronic acids. It was shown that 2,6-dimethylphenylboronic acid could be synthesized with "one-pot" method while para-alkyl-phenylboronic acid could not. An optimized process for the synthesis of 2,6-dimethylphenylboronic acid was obtained by investigating the influence of the boronation reagent, reactant proportion and solvent on the yield. Meanwhile, the preliminary synthesis of 2-ethylphenylboric acid was investigated with "one-pot" method too. Each product was identified by mass spectrum, ¹HNMR, IR and HPLC.