Dehydrogenative Coupling Reactions with Guanidino‐Functionalized Aromatics

Dehydrogenative coupling (DC) reactions are of importance for the construction of new carbon‐element bonds in synthetic organic chemistry. In this work, we report on the synthesis and characterization of several redox‐active guanidino‐functionalized aromatic molecules (GFAs) for use in DC (C−C and C−O) reactions. In a systematic approach, we first characterize the new DC reagents in all relevant redox and protonation states, and compare their performance in competitive test proton‐coupled electron transfer (PCET) reactions. Then, their use in four different DC reactions with different mechanisms is evaluated. New redox‐active diguanidines are prepared, with the aim to optimize their proton‐coupled electron transfer properties. Then, their oxidized, dicationic redox states are applied in dehydrogenative coupling reactions, with radical cation (electron transfer) or arenium‐ion like (proton transfer) mechanisms. The molecules emerge as valuable (and in some cases superior) alternatives to traditionally applied benzoquinones such as DDQ.