Abstract
Benzoxaborolone, or 2-carboxyphenylboronic acid, forms a stable borolactone that engenders 10(4)-fold greater stability toward oxidation than more commonly used phenylboronic acids and benzoxaboroles. Importantly, this stability could enhance the pharmacological activity of boron-based small molecules. Here, we experimentally and computationally examined the impact of pendant electron-donating and electron-withdrawing groups on the oxidative stability of benzoxaborolone. We find that oxidation is faster with electron-donating groups and slower with electron-withdrawing groups, though the changes are <10(2)-fold. The effects are explicable by physical organic principles of aromatic activation/deactivation. The results demonstrate that even substituted benzoxaborolones are much more resistant to oxidation than common boronic acids and provide guidance for their continued development as pharmacophores.