Pd-Catalyzed Heteroannulation Using N -Arylureas as a Sterically Undemanding Ligand Platform.

We report the development of ureas as sterically undemanding pro-ligands for Pd catalysis. N -Arylureas outperform phosphine ligands for the Pd-catalyzed heteroannulation of N -tosyl- o -bromoanilines and 1,3-dienes, engaging diverse coupling partners for the preparation of 2-subsituted indolines, including sterically demanding substrates that have not previously been tolerated. Experimental and computational studies on model Pd-urea and Pd-ureate complexes are consistent with monodentate binding through the nonsubstituted nitrogen, which is uncommon for metal-ureate complexes.