Visible‐Light‐Promoted Photocatalytic B−C Coupling via a Boron‐Centered Carboranyl Radical: Facile Synthesis of B(3)‐Arylated o‐Carboranes

A visible-light-mediated in situ generation of a boron-centered carboranyl radical (o-C2 B10 H11(.)) has been described. With eosin Y as a photoredox catalyst, 3-diazonium-o-carborane tetrafluoroborate [3-N2-o-C2B10H11][BF4] was converted into the corresponding boron-centered carboranyl radical intermediate, which can undergo efficient electrophilic substitution reaction with a wide range of (hetero)arenes. This general and simple procedure provides a metal-free alternative for the synthesis of 3-(hetero)arylated-o-carboranes.