Mechanistic Insight Leads to a Ligand Which Facilitates the Palladium‐Catalyzed Formation of 2‐(Hetero)Arylaminooxazoles and 4‐(Hetero)Arylaminothiazoles

By using mechanistic insight, a new ligand (EPhos) for the palladium-catalyzed C-N cross-coupling between primary amines and aryl halides has been developed. Employing an isopropoxy group at the C3-position favors the C-bound isomer of the ligand-supported palladium(II) complexes and leads to significantly improved reactivity. The use of a catalyst system based on EPhos with NaOPh as a mild homogeneous base proved to be very effective in the formation of 4-arylaminothiazoles and highly functionalized 2-arylaminooxazoles. Previously, these were not readily accessible using palladium catalysis.