Unifying Electric Field Catalysis with the Inductive Effect, Electro-Inductive Effect, and Differential Solvation-Induced Catalysis

A conspicuous similarity exists among electric field (EF) catalysis, substituent effects, and differential solvation-induced catalysis. All of these influence electronic behavior by changing the electron density distributed within the molecule and effectively modulating the electron flow in a reaction to bring about catalysis or inhibition. Analogous effects on electron flow have been utilized to generate a unified Electric Field Equivalent (EFEq) value for substituents and solvents using the oxidative addition of aryl bromides to Pd in the Suzuki-Miyaura coupling as the model reaction. Phenyl bromide without any para-substituent is considered as the reference reaction to derive EFEq of substituents, and the gas-phase barrier for the same reaction is considered as the reference for solvents EFEq. The amount of EF needed to bring the catalysis or inhibition to the reference point is defined as EFEq. The EFEq for substituents is correlated with Hammett constants and the recently reported electro-inductive effect, where the electrodes act as functional groups. Catalysis originating from differential solvation also correlates with the EFEq of the solvents. The concept of EFEq, an additive quantity, is envisioned to act as a basic building block to connect the electronic effect of substituents and differential solvation to the emerging EF catalysis.