Pyrene-tagged chloro oximes as ambient-light-accelerated ligation agents

We demonstrate how a normally base-induced or transition-metal-catalyzed cycloaddition reaction can be executed without additives by equipping the reactant with a chromophore as a light-harvesting unit, able to exploit light to boost the reaction. Specifically, we generate a highly reactive nitrile oxide upon light irradiation which is able to undergo cycloaddition reactions with a wide range of substrates by introducing a pyrene unit into the oxime precursor. Commercially available LED setups, and even ambient light, were successfully employed to induce the cycloaddition. Our approach demonstrates that the careful design of light-harvesting chromophores can be a powerful tool to facilitate light-induced chemical transformations