Novel oxidative functionalizations using earth-abundant transition metals

点击翻译按钮获取中文摘要

The development of selective aerobic oxidations is fundamentally important to the chemical industry due to the abundance of molecular oxygen and the sustainable source of energy provided by its reduction to water. A particularly important group of oxidation reactions is the direct, one-step transfer of an oxygen or nitrogen atom to an inactivated organic substrate, which generates molecules that are typically used as fuels, solvents and lubricants or as building blocks in the synthesis of fine chemicals and pharmaceuticals. Also, these direct atom transfers avoid the intermediacy of wasteful protecting-group strategies. However, most current methods employ toxic metal ions or wasteful oxidants, which is undesired for scaled-up applications.******The mission of this research program is to develop new strategies for oxygen or nitrogen transfer to substrates using earth-abundant metal ions under conditions that are environmentally benign. This research will follow two main thrusts. (1): get inspiration from biological metal-containing enzymes that are efficient and selective at transferring oxygen from the air into substrates. (2): develop novel reagents and catalysts for oxygen and nitrogen transfers that are atom-economical and employ earth-abundant and non toxic metal ions such as iron and copper. We propose four research objectives:******- Objective 1: to prepare molecules that mimic the enzymes and study their structure and reactivity to develop more efficient and more selective catalysts. We will particularly focus on reactions that are involved in the degradation of aromatics in the environment.******- Objective 2: to prepare models of metal-radical adducts and study their coupling reactions with radical partners. Such reactions pertain to biology and are also important in synthetic strategies (for example the fabrication of polyphenylene ether at a multi-million ton scale or cross dehydrogenative couplings).******- Objective 3: to employ constrained redox-active ligands containing an nitrogen-oxygen bond to facilitate oxygen transfer. ******- Objective 4: to develop a new methodology to transfer nitrogen-containing groups on phenols and open a one-step access to aminophenol building blocks.******The common theme of this program is the use of redox-active ligands, i.e. ligands that possess their own redox properties. Although the structure of metal complexes with these ligands is well understood, the literature is scarce with reports of their reactivity. The novelty of our program stands in a systematic use of these ligands in the context of oxidation reactions, especially on phenols, which are currently underused by the industry because there is no good method to convert them efficiently and selectively to useful materials. Thus, the expected outcome of this work will be the understanding and development of new oxidative methods that will allow the industry to think of unused chemicals as new feedstock.