Reactivity of Boronic Acids toward Catechols in Aqueous Solution

Yota Suzuki, Daisuke Kusuyama, Tomoaki Sugaya, Satoshi Iwatsuki, Masahiko Inamo, Hideo D. Takagi, Koji Ishihara

Research output: Contribution to journalArticle

Abstract

Fundamental information on the reactivities of boronic acids toward catechols in aqueous solution is required in all the fields dealing with boronic acid. However, comprehensive studies on reactivity are often hindered by so-called "proton ambiguity," which makes it impossible for the rate constants of boronic acid and boronate ion to be determined separately. Herein, we set up two reaction systems without proton ambiguity: (1) Alizarin Red S and (2) Tiron with several boronic acids (RB(OH)2) with different pKas and performed kinetic and equilibrium studies on the reaction systems. It was shown that the logarithms of the rate constants of RB(OH)2 and its conjugate boronate ion (RB(OH)3 -) decreased and increased linearly, respectively, with increasing pKa of RB(OH)2 for both systems. Consequently, the reactivities of RB(OH)2 and RB(OH)3 - were reversed at high RB(OH)2 pKa. It was also shown that the bulky o- substituents of phenylboronic acids retarded the backward reactions, resulting in enhancement of the formation constants of boronic acid-catechol esters.

Original languageEnglish
Pages (from-to)5255-5264
Number of pages10
JournalJournal of Organic Chemistry
Volume85
Issue number8
DOIs
Publication statusPublished - 2020 Apr 17

ASJC Scopus subject areas

  • Organic Chemistry

Fingerprint Dive into the research topics of 'Reactivity of Boronic Acids toward Catechols in Aqueous Solution'. Together they form a unique fingerprint.

  • Cite this

    Suzuki, Y., Kusuyama, D., Sugaya, T., Iwatsuki, S., Inamo, M., Takagi, H. D., & Ishihara, K. (2020). Reactivity of Boronic Acids toward Catechols in Aqueous Solution. Journal of Organic Chemistry, 85(8), 5255-5264. https://doi.org/10.1021/acs.joc.9b03326