Allylic C-H Acetoxylation with a 4,5-Diazafluorenone-Ligated Palladium Catalyst: A Ligand-Based Strategy To Achieve Aerobic Catalytic Turnover

Pd-catalyzed C-H oxidation reactions often require the use of oxidants other than O-2. Here we demonstrate a ligand-based strategy to replace benzoquinone with O-2 as the stoichiometric oxidant in Pd-catalyzed allylic C-H acetoxylation. Use of 4,5-diazafluorenone (1) as an ancillary ligand for Pd(OAc)(2) enables terminal alkenes to be converted to linear allylic acetoxylation products in good yields and selectivity under 1 atm O-2. Mechanistic studies have revealed that 1 facilitates C-O reductive elimination from a pi-allyl Pd-II intermediate, thereby eliminating the requirement for benzoquinone in this key catalytic step.