A number of first-row transition metal salts catalyze deprotonative dimerization of acidic arenes. Under the atmosphere of oxygen, nickel, manganese, cobalt, and iron chlorides have been shown to dimerize five-and six-membered ring heterocycles as well as electron- poor arenes. Both tetramethylpiperidide and dicyclohexylamide bases can be employed; however, the former afford slightly higher yields.
