The First Boron-Tethered Radical Cyclizations and Intramolecular Homolytic Substitutions at Boron

5-, 6-, and even 7-exo-trig radical cyclizations (1→2) are possible by applying a new boron-tethering approach with alkenylboronic esters. For certain substitution patterns, a subsequent intramolecular homolytic substitution (SHi) reaction at boron occurs (2→3) and leads to rearranged products. The C−B bond of the intermediate boracycles is readily oxidized to give diol products.