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

Abstract

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 Pd⁰ precatalyst under aerobic reaction conditions leads to oxidation of Pd⁰ by O₂ 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.