Synthesis of 4,5-Disubstituted o-Phenylenediamines: An Enabling Platform for Electrochemical Evaluation of Intramolecular Concerted Proton–Electron Transfer Reactions

Proton-coupled electron transfer (PCET) reactions occur in many reactions of global importance, including H2 evolution, among other applications. Surprisingly, knowledge gaps remain in our fundamental understanding of PCET and CPET reactions. In recent studies graphitic electrode systems that are modified by o-phenylenediamines have been singled out as an ideal platform for studying single-site CPET. Although this CPET experimental platform has been established, synthetic access to 4,5-o- phenylenediamines remains limited. Herein we discuss three distinct synthetic strategies aimed toward developing a modular synthetic route to symmetrical and asymmetrical 4,5-o-phenylenediamines. We demonstrate the utility of 4,5-o-dinitrobenzenes as relatively stable precursors to 4,5-o- phenylenediamines and a modular route to make 4,5-o-phenylenediamines in just 2-4 steps from commercial material.