Electric-Field Catalysis of Iminium Chemistry

The catalysis of chemical reactions with externally applied electric fields (AEFs) is one of the big unfulfilled dreams in chemistry.Despite much effort and more promise, compatibility with practical organic synthesis conditions has remained elusive.To tackle this challenge, we have suggested shifting attention from the force itself to their consequences and constructing catalytic Helmholtz layers.In this study, we test the concept of Helmholtz layer catalysis with iminium chemistry.While conjugate addition with Jørgensen-Hayashi prolinol ethers was catalyzed by electric fields already without ion pairs added as Helmholtz components, thioureas added as ionpair breakers still increased electric-field catalysis (EFC) and enantioselectivity, and they entered the Goldilocks inverted region.The explanation of these intriguing findings is that reactive iminium intermediates assemble into catalytic Helmholtz layers, and that iminium EFC in the effective electric fields they generate operates by hydroxide-transfer catalysis, that is, coupled hydroxide binding and release.These mechanistically new concepts critically contribute to the development of a conceptual mechanistic framework for EFC with externally AEFs under organic synthesis conditions.They confirm differences, near orthogonality of EFC to established organic synthesis methodology and highlight the dependence of EFC mechanisms on the reaction of interest.