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50 Pharmaceutical Technology APIs, EXCIPIENTS, AND MANUFACTURING eBOOK 2021 P h a r mTe c h . c o m Development C hemists in academia and industry have been performing reactions that are initiated by heat or a chemical reagent for many centuries. Advancements in technology com- bined with the rediscovery of new 'reagentless' activa- tion methods—such as using light in photochemistry and electrons in electrochemistry—have changed the way researchers devise syn- thesis routes toward novel molecules and set up their experiments. Photochemistry has gained much recognition over the past 20 years, and this growing trend has led to the development of innovative, modular f low photochemistry systems that allow users to efficiently switch between chemistries—saving time and money. Historical background Photochemistry is a branch of science concerned with the chemical effects of light, and, in nature, it is the basis of photosynthesis. In chemistry, the fundamental aim is the selective activation of mol- ecules to promote novel chemical transformations that are cleaner and greener under mild conditions. Traditionally, natural light from the sun and mercury or xenon lamps were used to perform photo- chemical reactions—involving cycloadditions (1), cyclizations (2,3), rearrangements (4), and oxygenations—for the synthesis of natural products and molecules of interest in industries such as pharmaceu- ticals and agrochemicals, as well as in research institutions. Using photons from a broad spectrum of wavelengths served as a powerful tool to access singlet and triplet states for the conversion of simple structures into complex products inaccessible by thermal processes. Shining a Light on Photochemistry in Flow Andrew Mansfield The ever-increasing interest in photochemistry has inspired the development of innovative, modular flow photochemistry reactors. Andrew Mansfield is flow chemistry leader at Syrris. SERGEY YAROCHKIN - STOCK.ADOBE.COM