Heterogeneous Photochemical Process Intensification: Crystallization-Induced Dynamic Resolution of Amines

High Resolution Image Download MS PowerPoint Slide The scale-up of solid-containing photochemical reactions is inherently challenging due to issues of light scattering and mass transport, which reduce productive light absorption and decrease reaction rates. However, reactive crystallizations are frequently employed as elements of process design, where in situ precipitation of products can drive equilibria or streamline purification operations. Herein we describe the implementation of a photoredox-driven crystallization-induced dynamic resolution of a racemic amine on multidecagram scale. This study features a recirculating photoreactor that continuously filters the reaction slurry containing the crystallized product and returns the clarified soluble phase for further irradiation and crystallization. By reducing crystal holdup and mitigating light attenuation in the optically dense reaction mixture, this configuration shortens reaction times and accelerates enantioenrichment compared to non-recirculating setups, enabling 1000-fold intensification of the original conditions reported in batch.