Scalable Photoinduced Cycloaddition for the Synthesis of Biorelevant Oxazoles

The practical and scalable synthesis of bioactive oxazoles remains challenging due to the limitations of existing methods, which often rely on intramolecular cyclization, transition metal catalysis, or harsh reaction conditions. To overcome these issues, we have developed a photoflow-mediated [3 + 2] cycloaddition between diazo compounds and nitriles, enabling a streamlined and step-efficient approach to oxazole synthesis. This strategy has facilitated the scalable preparation of various oxazole-based alkaloids, including balsoxine, texamine, uguenenazole, pimprinine, and pimprinaphine, as well as drug precursors and deuterium-labeled oxazoles. By introducing a modular, benchtop flow process, our method significantly improves the scalability and accessibility of diverse bioactive oxazoles.