Allylic C-H acetoxylations are among the most widely studied palladium(II)-catalyzed C-H oxidation reactions. While the principal reaction steps are well established, key features of the catalytic mechanisms are poorly characterized, including the identity of the turnover-limiting step and the catalyst resting state. Here, we report a mechanistic study of aerobic allylic acetoxylation of allylbenzene with a catalyst system composed of Pd(OAc) 2 and 4,5-diazafluoren-9-one (DAF). The DAF ligand is unique in its ability to support aerobic catalytic turnover, even in the absence of benzoquinone or other co-catalysts. Herein, we describe operando spectroscopic analysis of the catalytic reaction using X-ray absorption and NMR spectroscopic methods that allow direct observation of the formation and decay of a palladium(I) species during the reaction. Kinetic studies reveal the presence of two distinct kinetic phases: (1) a burst phase, involving rapid formation of the allylic acetoxylation product and formation of the dimeric Pd I complex [Pd I (DAF)(OAc)] 2 , followed by (2) a post-burst phase that coincides with evolution of the catalyst resting state from the Pd I dimer into a π-allyl-Pd II species. The data provide unprecedented insights into the role of ancillary ligands in supporting catalytic turnover with O 2 as the stoichiometric oxidant and establish an important foundation for the development of improved catalysts for allylic oxidation reactions.