Selective Oxidative Methods For Dehydrogenative Coupling And Hydrogen Peroxide Generation

Chapter 1: para-Alkenyl phenols were homo-coupled in a biomimetic manner using vanadium Schiff-base catalysts with oxygen as the terminal oxidant. The intermediates formed after the initial C-O or C-C bond is formed could be trapped by a variety of nucleophiles such as water, alcohols, or amines. Mechanism experiments established that phenol binding to the vanadium catalyst is the chief factor that allows for the high selectivity. Based on this proposal, reaction conditions were rationally designed to preferentially give either the β-O or β-β homodimers. Chapter 2: The same vanadium catalysts from Chapter 1 were used for ortho-alkenyl phenol homocouplings to afford the natural product benzoxanthenone carpanone and analogs. It was found that the endo diastereomer corresponding to the natural product carpanone was the minor product. Instead, the exo product was afforded selectively, which is not observed in other reported couplings of these substrates. Chapter 3: The synthesis of the phenol trimer natural product pyrolaside B was completed in five steps in a 16% overall yield. The lynchpin of the synthesis was a novel copper catalyzed phenol trimerization/cyclization to form spiroketal trimers. Chapter 4: A screen was performed to affect a dehydrogenative C-O phenol homo-coupling transformation with an iron salen catalyst under a variety of conditions. A singular C-O homo-dimerization is reported with 4-methoxy-2-methyl-phenol using a chromium salen catalyst under aerobic conditions with modest yields. Chapter 5: Three major interconnected research drives in the domain of lignin degradation are disclosed: 1) Photocatalytic aerobic oxidation of organic substrates to generate hydrogen peroxide and carbonyls concomitantly, 2) Utilization of in situ generated hydrogen peroxide to perform an “aerobic” Baeyer-Villiger reaction, and 3) Photocatalytic degradation of lignin models using singlet oxygen generating photocatalysts. Chapter 6: Examples of dehydrogenative dicarbonyl-aryl coupling are presented using DDQ, Bobbitt’s salt, Mn(OAc)2 and hypervalent iodide reagents. A singular report of a dicarbonyl-phenol coupling is discussed using a catalytic iron system with t-BuOOH as the oxidant.