Ruthenium(II)-Catalyzed C-H Bond Activation and Functionalization

The catalytic functionalization of unreactive C-H bonds has recently brought a revolution in synthetic methodologies for the production of pharmaceuticals and natural products and for opening new routes to molecular materials and polymers. With excess of bromobenzene, the diarylated phenyloxazoline was obtained as the sole product. The key role of the PPh ligand is to favor the difficult oxidative addition step. It also appears to disfavor diarylation in some specific examples. The use of arylchlorides gave the diarylated product, whereas the reaction in the presence of aryl tosylates selectively yielded the monoarylated product. The triazoles were cleanly monoarylated with a broad range of arylbromides including electron-deficient, electron-rich, and heteroarylbromides. This catalytic system was proved to be efficient for other functional directing groups like oxazoline, pyridine, and pyrazole with less reactive arylchlorides. Furthermore, the use of a functional alkene as a substrate allowed for the stereoselective formation of trisubstituted alkene.