Visible Light-Driven, Room Temperature Heck-Type Reaction of Alkyl Halides with Styrene Derivatives Catalyzed by B₁₂ Complex

A visible light driven Heck-type coupling reaction of alkyl halides with styrene and its derivatives catalyzed by the cobalamin derivative (B₁₂) with the [Ru(bpy)₃]Cl₂ photosensitizer at room temperature is reported. The catalytic efficiencies of the B₁₂ 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 B₁₂ 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 B₁₂ provided a practical protocol for the synthetic organic chemistry of the B₁₂ catalyzed reaction system. (Figure presented.).