True Homogeneous “Ligand-Free” Catalysis in Mizoroki–Heck Mono- and Double Arylations with Nonreactive Aryl Chlorides

Distinguishing between true homogeneous and heterogeneous catalytic mechanisms in cross-coupling reactions is not well-understood. The main reason for this is the numerous interconversions of different Pd species during the reaction progress that can potentially provide the catalytic activity. Catalytic experiments with the determination of the differential selectivity were performed on pairs of competing aryl halides or alkenes in the Mizoroki–Heck mono- and following double arylations in order to determine if the nature of active species would be affected by varying the Pd precursors. No differences in the differential selectivity values were observed for the products of both mono- and double arylations. The selectivity patterns indicated an identical active catalyst in all experiments. As the characteristics of Pd interconversions are well described, the active Pd species of mono- and double Mizoroki–Heck arylations with nonreactive aryl chlorides were identified as dissolved Pd molecular complexes.