Secondary Phosphine Oxide Preligands for Palladium-Catalyzed C–H (Hetero)Arylations: Efficient Access to Pybox Ligands

C–H arylations of oxazolines were accom- plished with a well-defined palladium catalyst de- rived from a secondary bisdiamantyl phosphine oxide. The single-component secondary phosphine oxide (SPO)-palladium complex enabled C–H activa- tions with aryl bromides and challenging aryl chlor- ides in the absence of directing groups, setting the stage for the step-economical synthesis of pybox li- gands under racemization-free reaction conditions.