Versatile Relay and Cooperative Palladium(0) N‐Heterocyclic Carbene/Copper(I) N‐Heterocyclic Carbene Catalysis for the Synthesis of Tri‐ and Tetrasubstituted Alkenes

Abstract Two new and efficient dual catalytic procedures for the synthesis of tri‐ and tetrasubstituted alkenes using aryl bromides and chlorides are reported. The formation of these vinyl arenes occurs independently in a one‐pot relay and a one‐pot cooperative procedure using well‐defined Pd and Cu N ‐heterocyclic carbene (NHC) complexes. Mechanistic studies were performed to elucidate the key role of the solvent in each procedure as well as the formation of the key intermediate, [Cu(alkenylboron)(NHC)], which allows transmetalation with the Pd‐NHC co‐catalyst in the cooperative catalysis.