Electric-Field-Assisted Anion-π Catalysis.

This report focuses on the remote control of anion-π catalysis by electric fields. We have synthesized and immobilized anion-π catalysts to explore the addition reaction of malonic acid half thioesters to enolate acceptors on conductive indium tin oxide surfaces. Exposed to increasing electric fields, anion-π catalysts show an increase in activity and an inversion of selectivity. These changes originate from a more than 100-fold rate enhancement of the disfavored enolate addition reaction that coincides with an increase in selectivity of transition-state recognition by up to -14.8 kJ mol-1. The addition of nitrate with strong π affinity nullified (IC50 = 2.2 mM) the responsiveness of anion-π catalysts to electric fields. These results support that the polarization of the π-acidic naphthalenediimide surface in anion-π catalysts with electric fields increases the recognition of anionic intermediates and transition states on this polarized π surface, that is, the existence and relevance of electric-field-assisted anion-π catalysis.