ABSTRACT
In the past five years, we showed that heterogeneous Pd/C can catalyse Ullmann-type reactions of aryl iodides, bromides, and chlorides. Two reaction pathways are possible: Reductive coupling, where Pd2+ is generated and reduced back to Pd0, and oxidative coupling, which starts with Pd2+ and needs an oxidising agent. Different reagents can be used for closing the reductive coupling cycle, including HCO2-(3), H2 gas (4), Zn/H2O (5), and alcohols (6). The two pathways can even be joined, giving a tandem system that converges on one product (7). All of these examples, however, require an extra chemical reagent. In this short communication, we present a different approach, using electrochemistry to close the catalytic cycle (Figure 1, right).
