Development of an Electrochemically-Reversible Hydride Transfer Mediator for Electroorganic Synthesis

Abstract

Hantzsch’s ester or amide is commonly used as a stoichiometric hydride transfer reagent in organic synthesis. The goal of this research is to see if Hantzsch’s ester or amide can be converted into an electrochemically-reversible hydride transfer mediator. The first step in achieving this is to realize the reversible 2 electron, 1 proton reduction of the corresponding pyridinium, 1, as shown below. Normally reduction of pyridiniums such as 1 are chemically irreversible due to the dimerization of the initially formed uncharged radical. We believe the key to avoid this pathway is to add a H-donor that can H-bond to the carbonyl O’s in such a way that an acidic H is properly positioned to H-bond to the radical, facilitating a second electron-transfer, proton-transfer step to generate the hydride donor. This presentation will describe the results of our initial efforts to achieve reversibility in this system. Figure 1