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

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posted on 03.11.2010 by Alison N. Campbell, Paul B. White, Ilia A. Guzei, Shannon S. Stahl
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−PdII intermediate, thereby eliminating the requirement for benzoquinone in this key catalytic step.