Book Description

Chemical copper-catalyzed aerobic oxidation reactions exhibit complexities not present in similar oxidation reactions employing noble metal catalysts with traditional chemical oxidants like hypervalent iodines or peroxides. The oxidation of organic molecules involves the removal of two protons and two electrons. This inevitably requires two CuII catalyst molecules to participate in the net oxidation reaction due to the one-electron redox-state changes typically associated with Cu. Additionally, CuI must react with molecular oxygen, a ground-state triplet molecule and net four-electron oxidant, to regenerate the active CuII catalyst. Aspects of these complexities are addressed in this thesis. Nature has evolved to use Cu catalysts (often together with redox-active organic cocatalysts) to perform oxidation reactions that use O2 as the terminal oxidant. The oxidation of CuI by O2 has been the subject of extensive investigation over the past several decades, and many of these studies were inspired by enzyme active sites in biological systems. Biological systems have also revealed pathways whereby CuII can oxidize organic substrates, and several chemical Cu-based catalyst systems exhibit intriguing similarities to enzymatic active sites. Herein, studies of several chemical copper-catalyzed aerobic oxidation reactions are reported, and, in many cases, the reactivity is compared to closely related enzymatic reactions. Chapter 1 summarizes challenges, opportunities, and progress made by our research group toward achieving selective and efficient Cu-catalyzed aerobic oxidation reactions. Chapter 2 describes a mechanistic study of aerobic alcohol oxidation catalyzed by Cu together with redox-active organic azodicarboxylates. Chapter 3 explains how Cu produces a redox-active organic nitroxyl cocatalyst under catalytic conditions from a simple diamine precursor. Chapter 4 details the investigation of single-electron transfer from phenol substrates to CuII.