Enhanced activity of bulky N-heterocyclic carbenes in nickel-NHC catalyzed Kumada-Corriu cross-coupling of aryl tosylates

Over the last decades, advances in Ni catalysis have expanded the chemical reactivity of cross-coupling reactions and led to the discovery of catalytic systems that are now widely applied in industrial and academic research. Herein, we report the cross-coupling of aryl tosylates by Ni-NHC catalysis using bulky N-heterocyclic carbene ligands. A notable feature of this operationally-simple method is the combination of 'fluoride effect' to minimize homocoupling and bulky NHC ligands, such as IPr* and IPr*(MeO), that enhance the activity of Ni in cross-coupling and prevent hydrolysis of sensitive oxygen electrophiles. A broad range of aryl and heteroaryl tosylates underwent cross-coupling with high efficiency. The finding that easily accessible, bulky NHCs with flexible CHPh2 wingtips enhance the reactivity in Ni-NHC cross-coupling represents a powerful approach for catalysis.