Copper triflate Ullmann reaction

Activation of Aryl Halides. Ullmann coupling of o-bromoni-trobenzene is accomplished under exceptionally mild conditions and in homogeneous solution by reaction with copper(I) triflate in the presence of aqueous NH3 (eq 41). Yields are enhanced by the presence of a small quantity of copper(II) triflate. That the reaction is diverted to reductive dehalogenation by ammonium tetrafluoroborate is presumptive evidence for an organocopper intermediate that can be captured by protonation. 

---