Response of reaction mechanisms to electric-field catalysis on carbon nanotubes in microfluidic reactors

Abstract

If accessible under scalable bulk conditions, remote control of charge translocation during a molecular transformation with oriented external electric fields promises to make a major contribution to sustainable organic synthesis. Here, we show that the combination of electric-field catalysis with anion–π and cation–π catalysis on carbon nanotubes in electromicrofluidic devices can influence reaction mechanisms under scalable bulk conditions. At high voltage, epoxide-opening ether cyclizations that do not occur without electric fields proceed to completion. Sensitivity to the orientation of the applied field indicates the nature of the rate-limiting motif in the transition state. Increasing magnitude of the electric field can change reaction mechanisms and accelerate the intrinsically disfavored pathways. Substrate positioning on the polarized nanotube surfaces enhances electric-field control over reaction mechanism. These results support the promise of electric-field anion–π and cation–π catalysis on carbon nanotubes in electromicrofluidic devices for use in organic synthesis.