Organocatalytic Microfluidic Double-Layer Capacitors.

Abstract

Ideas to use external electric fields to enable, accelerate and direct the movement of electrons during chemical reactions are not new. Theory and experiments under special conditions predict that electric-field catalysis (EFC) from externally applied fields could change the way we make molecules. The challenge is the incompatibility with organic synthesis under scalable bulk conditions. Access to applied electric fields (AEFs) > 1 V nm^-1, predicted as necessary for direct transition-state stabilization, is not possible even with electromicrofluidic systems, where the distance between the plate electrodes is minimized. Therefore, we decided to shift our attention from the applied fields to their consequences. We consider electrical double layers (EDLs) that form within a few nanometers from the plate electrodes as engineerable supramolecular electrodes. Applying lessons from cell-penetrating peptides (CPPs), we report supramolecular electrodes with effective electric fields (EEFs) that exceed applied fields by more than five million. According to a proline-catalyzed aldol condensation installed as benchmark reaction, those engineered from polyarginine and pyrenebutyrate are most active for EFC, exactly as in cellular uptake. With the best supramolecular electrodes, EFC triples the yield of one of the most optimized reactions in organocatalysis. New methods to access scalable EFC open up broad perspectives in organic synthesis and beyond.