Direct Synthesis of Hydroquinones from Quinones through Sequential and Continuous‐Flow Hydrogenation‐Derivatization Using Heterogeneous Au–Pt Nanoparticles as Catalysts

Organophotocatalytic Aerobic Oxygenation of Phenols in a Visible-Light Continuous-Flow Photoreactor

A mild photocatalytic phenol oxygenation enabled by a continuous-flow photoreactor using visible light and pressurized air is described herein. Products for wide-ranging applications, including the synthesis of vitamins, were obtained in high yields by precisely controlling principal process parameters. The reactor design permits low organophotocatalyst loadings to generate singlet oxygen. It is anticipated that the efficient aerobic phenol oxygenation to benzoquinones and p-quinols contributes to sustainable synthesis.

Recent Progress in Continuous-Flow Hydrogenation

To achieve a safe, efficient, and sustainable (even fully automated) production for the continuous-flow hydrogenation reactions, which is among the most often used reactions in chemical synthesis, new catalyst types and immobilization methods as well as flow reactors and technologies have been developed over the last years; in addition, these approaches have been combined with new and transformational technologies in other fields such as artificial intelligence. Thus, attention from academic and industry practitioners has increasingly focused on improving the performance of hydrogenation in flow mode by reducing the reaction times, increasing selectivities, and achieve safe operation. This Minireview aims to summarize the most recent research results on this topic with focus on the advantages, current limitations, and future directions of flow chemistry.