Benzoic Acid: Electrode-Regenerated Molecular Catalyst to Boost Cycloolefin Epoxidation.

Stoichiometric oxidants are always consumed in organic oxidation reactions. For example, olefins react with peroxy acids to be converted to epoxy, while the oxidant, peroxy acid, is downgraded to carboxylic acid. In this paper, we aim to regenerate carboxylic acid into peroxy acid through electric water splitting at the anode, in order to construct an electrochemical catalytic cycle to accomplish the cycloolefin epoxidation reaction. Benzoic acid, which can be strongly adsorbed onto the anode and rapidly converted to peroxy acid, was selected to catalyze the cycloolefin epoxidation. Furthermore, the peroxybenzoic acid will be further activated on the electrode to fulfill the epoxidation and release the benzoic acid to complete the catalytic cycle. In this designed reaction cycle, benzoic acid acts as a molecular catalyst with the assistance of the electrode-generated reactive oxygen species (ROS). This method can successfully reform the consumable oxidants to molecular catalysts, which can be generalized to other green organic syntheses.