We have been trying to introduce new selectivity into electrochemical reactions by modifying the surface of an electrode and then confining chemical reactions to the region of the reaction close to that surface. The goal is to translate the extremely high levels of site-selectivity seen in chemical reactions on a microelectrode array into a tool for preparative synthetic reactions. Previously, in series of competition studies between electron-rich and electron-poor benzyl alcohol substrates, we found the oxidation always favor the electron-rich benzyl alcohol to aldehyde, with the help of diblock copolymer coated electrode and confining agent (Scheme 1). By applying larger amount of confining agent or more reactive mediator, we learned how to optimize the selectivity to higher level. It is clear that a molecular recognition event on the surface of the electrode could be used to control the selectivity of the reaction.<br/><br/>Knowing the diblock copolymer’s ability to select electron-rich aryl rings, the origin of this selectivity and how it induces selectivity have been studied. Based on experimental evidence, hydrophobic pocket interactions between polymer and substrates might be the explanation for selectivity. In order to better utilize these hydrophobic interactions, we targeted on the remote selectivity inducement. By separating the recognition center and reaction center, we used polymer to recognize one side of molecule and let mediator react on the other side. From new series of aromatic substituted cyclohexanol competition studies, we observed remote effect of an electron-rich aromatic group contributed to the alcohol oxidation (Scheme 2). After optimizing reaction conditions, we achieved a chemoselectivity in electrochemical reaction which nonelectrochemical mediators cannot obtain.

New method to control selectivity in electrochemical reactions by modifying electrode surface

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