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

Abstract

Pd-catalyzed C−H oxidation reactions often require the use of oxidants other than O₂. Here we demonstrate a ligand-based strategy to replace benzoquinone with O₂ 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 O₂. Mechanistic studies have revealed that 1 facilitates C−O reductive elimination from a π-allyl−Pd^II intermediate, thereby eliminating the requirement for benzoquinone in this key catalytic step.