Microreactor technology for green and sustainable photo– and organo– catalytic synthesis

Abstract

In recent years, the application of microfluidic devices demonstrated significant promise as a novel method in organic chemistry. One of the research fields in which microfluidics have shown a great potential is visible light photoredox catalysis. The implementation of microreactors offers considerable advantages over the batch reactor as follows: a more predictable reaction scale-up, ecreased safety hazards, preserves atom economy, improved reproducibility and yields, and decreased energy consumption. The high surface-area-to-volume ratios provide more efficient irradiation of a reaction mixture, reduction of irradiation times, and hence prevention of undesired side reactions. As a result, enhanced selectivity, product purity, and lower catalyst loading are achieved, which leads to overall more sustainable and greener processes. Even though significant rogress has been achieved, greener alternatives to many common industrial processes still remain elusive, especially in the fine chemicals industry. To perform rocesses greener and cheaper, catalysis is a key tool to reduce energy consumption and develop more atom-economical transformations. To show the potential use of microdevices in organic synthesis, we have applied microfluidic chemistry in mutual photoredox and organocatalytic synthesis of the functionalized tetrahydroisoquinoline, a biologically active compound with interesting pharmaceutical properties. The results obtained in microreactor devices were compared with those obtained in batch reactions and it was demonstrated that microreactors can achieve superb yields and decreased waste generation. Thus, microflow photochemistry unambiguously has demonstrated its superiority over conventional reactor systems and its potential as green technology in synthesis processes.