Transition-Metal-Free Borylation of Aryl Bromide Using a Simple Diboron Source
Taeho Lim, Jeong Yup Ryoo and Min Su Han*
*Department of Chemistry, Gwangju Institute of Science and Technology (GIST), Gwangju 61005, Republic of Korea,
Email: Happyhan
gist.ac.kr
T. Lim, J. Y. Ryoo, M. S. Han, J. Org. Chem., 2020, 85, 10966-10972.
DOI: 10.1021/acs.joc.0c01065
Abstract
A simple transition-metal-free borylation reaction of aryl bromides with bis-boronic acid (BBA) provides arylboronic acids at mild temperatures directly without any deprotection steps and purified by conversion to trifluoroborate salts. The functional group tolerance was considerably high.
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Details
This study presents a novel, transition-metal-free borylation reaction of aryl bromides using bis-boronic acid (BBA) as a simple diboron source. The reaction is performed under mild conditions with t-BuOK as the base, converting aryl bromides directly to arylboronic acids without requiring deprotection steps. The method demonstrates high functional group tolerance and yields, with products often isolated as stable potassium trifluoroborate salts. The reaction mechanism likely involves a radical pathway, as indicated by radical-trapping experiments. This approach addresses limitations of traditional transition-metal-catalyzed borylation methods, such as the need for air- and moisture-sensitive, expensive catalysts, and potential metal residue in products. The optimized conditions include using MeOH as the solvent and maintaining a low temperature (0°C) to enhance yields. The study's findings offer a practical and efficient method for synthesizing arylboronic acids, which are valuable in various organic reactions and research fields. This method is particularly advantageous for its simplicity, cost-effectiveness, and the elimination of transition-metal catalysts, making it a significant advancement in the preparation of organoboron compounds.
Key Words
ID: J42-Y2020
