Continuous Flow Synthesis of Substituted 3,4-Propylenedioxythiophene Derivatives

We report a continuous flow method for the process intensification of commercially important propylenedioxythiophene (ProDOT) monomers. A new four-step synthetic route was designed to make the whole process more economical and continuous flow amenable. Apart from being safe and having a higher throughput via continuous flow, we could optimize each of the synthetic steps to quantitative conversion. GC–MS analysis was used to monitor each of the processes during optimization. The overall process could be completed in around 65 min, starting from the commercially available materials, as compared to the few days via the reported batch processes. Furthermore, we have shown that the most critical step of the Williamson etherification could be intensified via continuous flow to the space–time yield (STY) of 63 g/h/L as compared to 0.16 g/h/L via the traditional batch process. As all the synthetic steps in our continuous flow process were optimized to quantitative conversions, it opens up the possibility of telescoping of the whole process. We believe that our findings will be able to fill the existing gap in the process intensification for the synthesis of commercially important ProDOT-based monomers.