Continuous flow photochemistry and green chemistry

INTRODUCTION
Performing chemical reactions under photochemical conditions is considered an inherently sustainable means to generate target structures of interest. The ability to trigger a vast variety of transformations photochemically, whereby selectivity arises from finetuning the wavelength and intensity of light, offers great control over a given process. Moreover, photons are seen as traceless reagent equivalents that could replace stoichiometric reagents or act in tandem with bespoke photocatalysts to bring about the green synthesis of drug-like target structures and important chemical building blocks alike (1).

Over a century ago, the pioneering work of Ciamician, who is rightly considered as one of the pioneers of synthetic photochemistry, laid the foundations for modern photochemistry by showcasing how many new chemical transformations can be achieved using light. In his 1912 landmark paper on the future of photochemistry, Ciamician outlines how this technology holds the potential to establish chemical synthesis independent of fossil sources of energy and related organic building blocks (2). Despite this vision photochemistry failed in establishing itself as the method of choice for the green synthesis of organic molecules and only recent developments, a century later, have reinvigorated a substantial interest in this field.