Photocatalytic Arylations with Diazonium Salts in Aqueous and Biorelevant Media

Abstract Performing designed, abiotic chemical transformations in live environments represents a powerful approach to interrogate and manipulate biology, and to uncover new types of biomedical tools. Despite significant advances in the area, the list of bio‐orthogonal reactions so far available is still very short, and mainly restricted to the use of strained reactants, or metal‐promoted processes. En route to further expanding the repertoire of biocompatible reactions, we demonstrate here that aryldiazonium salts, well‐established as radical precursors, can react with unsaturated systems in biologically relevant media under photocatalytic conditions, to give either addition or cycloaddition products, depending on the reactants.