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A Water-Stable Boronate Ester Cage
journal contributionposted on 2024-02-08, 01:04 authored by Philipp H. Kirchner, Louis Schramm, Svetlana Ivanova, Kazutaka Shoyama, Frank Würthner, Florian Beuerle
The reversible condensation of catechols and boronic acids to boronate esters is a paradigm reaction in dynamic covalent chemistry. However, facile backward hydrolysis is detrimental for stability and has so far prevented applications for boronate-based materials. Here, we introduce cubic boronate ester cages 6 derived from hexahydroxy tribenzotriquinacenes and phenylene diboronic acids with ortho-t-butyl substituents. Due to steric shielding, dynamic exchange at the Lewis acidic boron sites is feasible only under acid or base catalysis but fully prevented at neutral conditions. For the first time, boronate ester cages 6 tolerate substantial amounts of water or alcohols both in solution and solid state. The unprecedented applicability of these materials under ambient and aqueous conditions is showcased by efficient encapsulation and on-demand release of β-carotene dyes and heterogeneous water oxidation catalysis after the encapsulation of ruthenium catalysts.
tolerate substantial amountsfacile backward hydrolysis>- butyl substituentsphenylene diboronic acidsfar prevented applicationsdynamic covalent chemistryboronate ester cages6 bfully preventeddynamic exchangeboronic acidsunprecedented applicabilitysteric shieldingsolid stateruthenium catalystsreversible condensationparadigm reactionortho neutral conditionshexahydroxy tribenzotriquinacenesfirst timedemand releasecarotene dyesboronate estersbase catalysisaqueous conditions