Issue Date: January 19, 2015
Nickel Shines In Ammonia Couplings
By developing a stable nickel catalyst system, a Canadian research team has fulfilled a quest to move beyond using expensive palladium catalysts in cross-coupling reactions to make aryl amines from ammonia. Ammonia is the simplest and most abundant N–H source in chemistry, with virtually all synthetic nitrogen-containing compounds originating from the inexpensive feedstock. Industrial syntheses of amines from ammonia, however, typically require heterogeneous catalysts at relatively high temperatures and pressures, which results in modest product selectivity. Only recently have chemists devised homogeneous palladium catalysts for the task, which allow for more selective ammonia couplings under milder conditions. The approach taken by Andrey Borzenko, Mark Stradiotto, and coworkers of Dalhousie University, in Halifax, Nova Scotia, is the first example of nickel-catalyzed arylation of ammonia to make amines. The researchers used air-stable Ni(cyclooctadiene)2 or NiCl2(dimethoxyethane) with a ferrocenyl phosphine ligand known as JosiPhos to link up a range of substituted aryl and heteroaryl bromides, chlorides, and tosylates with ammonia (one shown) to make diverse aryl and heteroaryl amines (Angew. Chem. Int. Ed. 2015, DOI: 10.1002/anie.201410875).
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