Visible-Light Photoredox Catalysis in Flow

Angewandte Chemie 51(17), 4144-4147, DOI: 10.1002/anie.201200961

Photoredox catalysts have recently been used 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.1 The development of methods based on the single-electron transfer properties of photoredox catalysts, particularly in the last several years, has represented a shift in models with respect to the way synthetic chemists consider both photochemistry and redox manipulations of organic molecules.2–4In 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.5, 6 Conducting transformations in flow has many advantages compared to the more traditional batch reactions, in particular: a 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.7 Due to this feature, we reasoned that a mesofluidic photochemical flow reactor would be amenable to our group’s ongoing study of visible-light-induced organic transformations mediated by photoredox catalysts.