Vitamin B₁₂ in Photocatalysis - An Underexplored Frontier in Cooperative Catalysis

Vitamin B₁₂ (VB₁₂) is a flexible and sustainable catalyst both in nature and the reaction flask, facilitating varied organic transformations of high value to both enzymatic processes and synthetic chemists. Key to this value is the breadth of reactivity it possesses, capable of both ionic, 2 electron chemistry, and radical, 1 electron chemistry. In particular, the ability to generate carbon-centered radical intermediates via photolysis of organocobalt intermediates formed from alkyl electrophiles opens the door to powerful new radical transformations challenging to achieve using classical photoredox or ligand-to-metal charge transfer (LMCT) catalysis. While this unique photocatalytic reactivity of VB₁₂ has been increasingly leveraged in monocatalytic schemes, recent reports have demonstrated VB₁₂ is able to function as the photocatalytic component in cooperative schemes, driving diverse reactivity including remote elimination of alkyl halides, regioselective epoxide arylation, and regioselective epoxide reduction. This concept briefly overviews the enabling photochemical properties of VB₁₂ and recent applications in cooperative catalysis, providing a framework for the continued development of new cooperative catalyst systems using this powerful photoactive complex.