Dynamic Spinning Disc Reactor Technology to Enable In Situ Solid Product Formation in a Diazotization and Azo Coupling Sequence

Solid-forming reactions are notoriously challenging to process in standard flow processes. Even though the formation of a solid product within a reaction can facilitate simple purification, homogeneous reactions are often utilized to enable flow processing. We report the application of dynamic spinning disc reactor (SDR) technology as a strategy to handle in situ solid product formation while handling exothermic chemistry. The system is exemplified by using a diazotization and azo coupling reaction system. Advantages of the approach include the use of water as the sole reaction solvent, mild operating conditions (20 °C), and a simple isolation procedure by filtration and drying. We demonstrate that stable operation of the system is possible for 120 min, affording 55.9 g of Sudan II.