Enhancing N-arylation productivity: the amplified potential of electrophotocatalysis in flow.

The recent advances in the area of electrophotocatalysis (EPC) show that it is a highly suitable technique to yield greener and more sustainable organic synthesis. The overall productivity of EPC however is constrained by a multitude of practical limitations, which impose difficulties in effectively harmonizing the photochemical and electrochemical steps, let alone in accelerating both steps simultaneously. In this contribution, we have tackled these limitations by developing a parallel plate flow cell that permits the execution of EPC in continuous flow. By using a transparent electrode, such as fluorine-doped tin oxide (FTO) or indium tin oxide (ITO) coated glass, the interelectrode distance could be reduced while improving photon absorption. By enhancing both the photochemical and electrochemical steps simultaneously, a notable increase in productivity and space–time-yield (a ten-fold and 300-fold improvement, respectively) of the N-arylation of different azoles was observed. In addition, this was achieved in a single-pass process under electrolyte-free conditions. Highlights: • We have created a flow cell that incorporates a transparent electrode, allowing simultaneous photochemical and electrochemical activation. • By using a parallel energy input, a productivity increase for the N-arylation of different azoles under electrolyte-free conditions was observed. • A single pass sufficed to reach high conversions, rendering this a true continuous flow process. [ABSTRACT FROM AUTHOR]