Photo-Flow Technology for Chemical Rearrangements: A Powerful Tool to Generate Pharmaceutically Relevant Compounds

In recent years, photochemistry has increasingly emerged as an enabling methodology in both academia and the pharmaceutical industry. Long photolysis times and the gradual reduction of light penetration remained for many years unsolved issues for photochemical rearrangements, triggering the generation of highly reactive species in an uncontrolled fashion and causing the formation of multiple side products. The emergence of continuous-flow chemistry significantly helped to overcome these issues, thus prompting the implementation of photo-flow-based approaches for the generation of pharmaceutically relevant substructures. This Technology Note highlights the benefits of flow chemistry for photochemical rearrangements, including Wolff, Favorskii, Beckmann, Fries, and Claisen rearrangements. We showcase recent advances for photo-rearrangements in continuous flow applied to the synthesis of privileged scaffolds and active pharmaceutical ingredients.