Phenolate Enabled General and Selective Fe/Ti Cocatalyzed Biaryl Cross-Couplings between Aryl Halides and Aryl Grignard Reagents.

The serendipitous addition of a phenolate to FeCl3/TMEDA/Ti(OEt)4 enables a strong Fe/Ti cooperativity that can efficiently catalyze a general and selective biaryl-coupling reaction. In the absence of phosphine or NHC ligands, various aryl chlorides, bromides, and iodides can couple with a variety of common and Knochel-type aryl Grignard reagents. A wide range of sensitive functional groups in either coupling partner can be tolerated. This bimetallic cocatalysis not only remarkably extends the scope of Fe-catalyzed biaryl couplings but also provides a solution to the problem of functional group compatibility of Grignard reagents.