Investigations into the Role of 4,5-Diazafluorenone in Aerobic Palladium Catalyzed Oxidations

Aerobic palladium catalyzed oxidation reactions proceed through an oxidase-style mechanism where dioxygen is used as a terminal oxidant and PdII performs substrate oxidation. Ligands are often employed to help facilitate Pd0 reoxidation but ligands also decrease the electrophilicity of PdII which is important for substrate oxidation. Understanding the balance between PdII electrophilicity and Pd0 stabilization is important for performing efficient aerobic Pd-catalysis. Aerobic catalysis often employs pyridine derived ligands that strongly coordinate to PdII and inhibit substrate catalysis. 4,5-Diazafluoren-9-one (DAF) has been identified as a unique ligand for aerobic catalysis that enables very efficient aerobic turn over as well as substrate oxidation. This thesis is an in-depth investigation of how DAF promotes aerobic palladium oxidation catalysis.;Chapter 1 highlights the mechanistic aspects of palladium catalyzed alkene oxygenation as well as palladium catalyzed allylic C-H acyloxylation. Chapter 2 is a review of all of the recent reactions that have been developed that utilize DAF as a ligand. Chapter 3 is an extensive study of the coordination chemistry of DAF with Pd(OAc)2 as well as permutations of DAF and PdII carboxylates that have been utilized in catalysis previously. Chapter 4 explores the implications of the coordination chemistry in the context of the intramolecular aza-Wacker reaction. Chapter 5 reports the characterization a novel DAF ligated PdI species that forms in both the intramolecular aza-Wacker reaction as well as the acetoxylation reaction and explores its implications in catalysis. Chapter 6 is a kinetic mechanistic investigation of the DAF-promoted allylic C-H acetoxylation reaction in which the resting state of the catalyst is investigated using X-ray absorption spectroscopy and NMR spectroscopy.