Aerobic Acyloxylation of Allylic C-H Bonds Initiated by a Pd0 Precatalyst with 4,5-Diazafluoren-9-one as an Ancillary Ligand

Palladium-catalyzed allylic C-H oxidation has been widely studied, but most precedents use acetic acid as the coupling partner. In this study, a method compatible with diverse carboxylic acid partners has been developed. Use of a Pd-0 precatalyst under aerobic reaction conditions leads to oxidation of Pd-0 by O-2 in the presence of the desired carboxylic acid to generate a Pd-II dicarboxylate that promotes acyloxylation of the allylic C-H bond. Good-to-excellent yields are obtained with a roughly 1:1 ratio of the alkene and carboxylic acid reagents. Optimized reaction conditions employ 4,5-diazafluoren-9-one (DAF) as a ligand, in combination with a quinone/iron phthalocyanine cocatalyst system to support aerobic catalytic turnover.