Catalytic Insertion of Pd–Vinylidenes Into B─H Bonds

An unprecedented palladium (Pd)‑catalyzed insertion of unsaturated carbenes into B─H bonds is described. Using alkynyl hypervalent iodine reagents as carbene precursors and amine–borane adducts as boron sources, this method delivers a broad range of E ‑configured alkenyl monoborinates in good‐to‐high yields with exceptional stereoselectivity (>20:1 E/Z ). The reaction proceeds under mild conditions, tolerates diverse aromatic, heteroaromatic, and aliphatic substituents, and is readily scalable to gram quantities. The resulting monoboronate products participate efficiently in a variety of C─X bond‑forming transformations, underscoring their synthetic versatility. Initial mechanistic investigations and DFT calculation support the formation of an unsaturated Pd–vinylidene intermediate, with stereocontrol influenced by ligand coordination at the palladium center. Collectively, this work establishes a mechanistic and conceptual bridge between unsaturated carbene chemistry and organoboron synthesis, expanding the reactivity landscape of Pd‑‐carbene intermediates.