The Copper-Catalyzed Ullmann Coupling Reaction

The copper-mediated Ullmann reaction has been a stalwart method for the synthesis of aryl ethers for decades. Its principal drawbacks are the need for stoichiometric quantities of copper and harsh reaction conditions [12d[. 

The same year, Sekar s group [119] demonstrated the arylation of phenols with aryl bromides using a 2,2 -Bis(diphenylphosphinoamino)-l,l -binaphthyl (BINAM)-copper(ll) catalytic system. 

Shingare and coworkers [120] reported the use of tris-(2-aminoethyl)amine as a novel and efficient tripod ligand for the Cu(I)-catalyzed (at 10 mol% loading) arylation of a plethora of phenols with aryl 

Wang and Franzen [121c] in 2012 reported a Cu(I) intramolecular arylation that tifForded useful and desirable 2-aryl-substituted chromans using hydroxyalkyl-substituted aryl bromides. Cul (10 mol%) and 2-aminopyridine (20 mol%) as ligand were used at 100 °C in diglyme with NaOMe as base. The yields were generally good. 

In an effort to develop more sustainable versions of this reaction, the following innovations have been made, which we have selected for discussion here. 

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