Direct Access to Acylboranes via Formal Condensation of Carboxylic Acids with Ligated Boranes

The unique synthetic potential of acylboron species has long attracted attention from the synthetic chemistry community, but their broader application has been limited by challenges associated with their preparation. In this work, we report a mechanistically distinct radical-based C(acyl)-B cross-coupling strategy that enables a "formal condensation" between readily available carboxylic acids and easily accessible ligated boranes. The success of this transformation relies on the distinctive use of a phosphonite ligand, which achieves an optimal balance between the stability and reactivity of the borane moiety. This method demonstrates a broad substrate scope with high practical utility, and its strategic value has been further highlighted through diverse downstream derivatizations of the resulting acylborane compounds.