Iron-Catalyzed Borylation of Propargylic Acetates for the Synthesis of Multisubstituted Allenylboronates.

A novel iron-catalyzed borylation of propargylic acetates leading to allenylboronates has been developed. The method allows the preparation of a variety of di-, tri- and tetrasubstituted allenylboronates at room temperature with good functional group compatibility. Stereochemical studies show that an anti-S 2' displacement of acetate by boron occurs; this also allows transfer of chirality to yield enantiomerically enriched allenylboronates.