Photoinduced Ullmann C−N Coupling: Demonstrating the Viability of a Radical Pathway

Sidney E. Creutz,1* Kenneth J. Lotito,1* Gregory C. Fu,1,2† Jonas C. Peters 

http://www.sciencemag.org/content/338/6107/647.short 

In this paper, the authors demonstrate the viability of a radical-based mechanism in Ullmann C-N coupling.  As in traditional Ullmann coupling, the reaction involves a copper reagent, but in the present report, the reaction is driven by light.  This allows the reaction to be carried out at or below RT, and substoichiometric amounts of copper do a reasonably good job (10% [Cu] affords 64% yield).  This report contrasts the one by Hartwig in 2008 which demonstrated ox.add. based Ullmann coupling.