Potassium haloalkyltrifluoroborate salts: synthesis, application, and reversible ligand replacement with MIDA

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• 作者：Sarah J. Burke ; James M. Gamrat ; Jacqueline R. Santhouse ; Dylan T. Tomares ; John W. Tomsho ; ^{j.tomsho@usciences.edu" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Boronic acid ; Boronic ester ; Potassium trifluoroborate ; Dichloroborane ; Hydroboration ; MIDA boronate
• 刊名：Tetrahedron Letters
• 出版年：2015
• 出版时间：7 October 2015
• 年：2015
• 卷：56
• 期：41
• 页码：5500-5503
• 全文大小：967 K

文摘

Increased interest in boron-containing pharmaceuticals has created a need for efficient syntheses of organoboron compounds. This article describes one- and two-pot syntheses of potassium haloalkyltrifluoroborate salts, important building blocks for the incorporation of boron into complex molecules. The sequential, high-yielding procedures (65% to 92%) involve hydroboration of commercially available haloalkenes with dichloroborane (prepared in situ from triethylsilane and boron trichloride), followed by treatment of the crude hydroboration products with potassium hydrogen difluoride. A hexaethyldisiloxane byproduct that hinders the isolation of the desired boronic acids and esters was identified and easily removed via this procedure. The value of the potassium haloalkyltrifluoroborate salts is subsequently demonstrated in example substitution reactions, which were followed by a reversible ligand replacement with N-methyliminodiacetic acid (MIDA). Reversibly switching these orthogonal boron protecting groups enables full exploitation of their favorable chemical properties, effectively bridging these platforms and further expanding their scope and utility.