Visible Light‐Driven, Room Temperature Heck‐Type Reaction of Alkyl Halides with Styrene Derivatives Catalyzed by B 12 Complex

A visible light driven Heck‐type coupling reaction of alkyl halides with styrene and its derivatives catalyzed by the cobalamin derivative (B 12 ) with the [Ru(bpy) 3 ]Cl 2 photosensitizer at room temperature is reported. The catalytic efficiencies of the B 12 catalyst were compared to that of other cobalt complexes such as cobaloxime. Various control experiments supported a radical‐based mechanism similar to those for typical B 12 model reactions. A unique coupling reaction combined with 1,2‐migration of the functional group is also reported. Mild reaction conditions using an environmentally benign cobalt catalyst derived from the natural B 12 provided a practical protocol for the synthetic organic chemistry of the B 12 catalyzed reaction system.