Chemists Spruce Up Nickel Aminations

Transition-metal-catalyzed cross-coupling reactions to construct carbon-carbon and carbon-heteroatom bonds are wildly successful. Palladium catalysts have dominated these reactions, but chemists are interested in switching to more abundant, lower-cost metals such as nickel that can operate under greener reaction conditions. To that end, Neil K. Garg and coworkers at UCLA developed a procedure last year for nickel-catalyzed Suzuki-Miyaura C–C couplings that uses a small amount of nickel with a simple ligand in the biobased solvent 2-methyltetrahydrofuran. The UCLA researchers have now developed a complementary method for forming aryl C–N bonds (ACS Catal. 2014, DOI: 10.1021/cs501045v). Their standard procedure calls for using as little as 1 mol % NiCl₂(dimethoxyethane) and a commercial N-heterocyclic carbene ligand along with a boronic acid and a base in ­2-methyltetrahydrofuran. The team has used the reaction to couple aryl sulfamates and aryl chlorides with morpholine and other cyclic amines to produce gram amounts of new heterocyclic compounds (one shown above). The research received kudos from the journal’s editors, who believe it will be of interest to medicinal chemists focused on identifying drug leads and process chemists looking to develop environmentally friendly routes to synthetic intermediates.