Visible-light photoredox catalysis in flow.

Photoredox catalysts have recently been utilized as powerful tools for synthetic chemists to exploit the energy gained by the absorption of low-energy light within the visible spectrum to initiate a variety of organic transformations. The development of methods based on the single electron transfer properties of photoredox catalysts, particularly in the last several years, has represented a paradigm shift with respect to the way synthetic chemists consider both photochemistry and redox manipulations of organic molecules. 2 , 3 , 4 In addition, the advent of new technologies has enabled chemists to conduct reactions with greater efficiency than ever before. Among these new technologies is the development and wide implementation of flow reactors. Conducting transformations in flow has many advantages compared to the more traditional batch reactions, in particular: more predictable reaction scale-up, decreased safety hazards, and improved reproducibility. In addition, for photochemical transformations, the high surface area to volume ratios typical of flow reactors allow for more efficient irradiation of a reaction mixture. Due to this feature, we reasoned that a