Dioxaborole

Dioxaborole is a class of organoboron compounds that feature a five-membered ring containing one boron atom and two adjacent oxygen atoms, collectively termed a 1,3,2-dioxaborolane motif. This ring can exist as a simple cyclic boronate ester derived from boronic acids and diols, or as part of larger fused systems such as benzoxaboroles, where the dioxaborolane ring is fused to an aromatic ring.

A notable member is tavaborole, a benzoxaborole antifungal agent approved for the topical treatment of onychomycosis. In tavaborole and related compounds, the boron center participates in reversible covalent interactions with biological targets, contributing to inhibition of fungal leucyl-tRNA synthetase and disruption of protein synthesis.

In organic synthesis, dioxaborolane rings provide versatile boron sources for cross-coupling reactions, particularly Suzuki–Miyaura couplings. The cyclic boronate esters are often more stable than simple boronic acids and can be used as protecting groups for boron reagents; they can be hydrolyzed to liberate the active boronic acid when desired.

Preparation generally involves condensation of a boronic acid with a diol, such as ethylene glycol or pinacol, to form the cyclic boronate ester. In benzoxaboroles, ring formation occurs through cyclization of an ortho-alkyl- or -aryl boron-containing precursor to yield the fused heterocycle.

Dioxaboroles are studied in medicinal chemistry and materials science for their unique boron-oxygen chemistry and Lewis acidity. Handling follows standard precautions for organoboron compounds, with attention to moisture sensitivity for many boronate esters. See also benzoxaborole, boronic acids, and Suzuki coupling.