Metal-Reductant-Free Electrochemical Nickel-Catalyzed Couplings of Aryl and Alkyl Bromides in Acetonitrile

While reductive cross-electrochemical coupling is an attractive approach for the synthesis of complex molecules at both small and large scale, two barriers for large-scale applications have remained: the use of stoichiometric metal reductants and a need for amide solvents. In this communication, new conditions that address these challenges are reported. The nickel catalyzed reductive cross-coupling of aryl bromides with alkyl bromides can be conducted in a divided electro-chemical cell using acetonitrile as the solvent and diisopropylamine as the sacrificial reductant to afford coupling products in synthetically useful yields (22-80%). Additionally, the use of a combination of the ligands 4,4',4-tri-tert-butyl-2,2':6',2'-terpyridine and 4,4'-di-tertbutyl-2,2'-bipyridine is essential to achieve high yields.