Facile Synthesis of Stable Haloalkylborons via Atom Transfer Radical Addition Using Sterically Hindered Vinyl‐Oxazaborolidinone

α‑Haloalkylboron compounds are valuable ambiphilic synthons, but the conventional ATRA reaction using vinyl‐Bpin often gives products that are unstable and difficult to isolate. In this study, we developed a copper‑catalyzed ATRA reaction using a sterically bulky protecting group, “OxB(oxazaborolidinone)”. OxB sterically shields the boron center while retaining the vacant p‑orbital necessary for stabilizing the radical intermediate. Using this method, we successfully synthesized stable α‑haloalkylboron compounds via the ATRA reaction of a wide range of primary, secondary, and tertiary alkyl halides with vinyl OxB. The resulting products are readily deprotected and can undergo diverse functional group transformations starting from the C─X and C─B bonds.