Earth Abundant Metals for Simple Coupling Reactions

可持续化学工艺的未来取决于催化剂的安全供应。由于大多数催化剂依赖于稀有、昂贵和有毒的铂族金属（PGMs），因此开发替代品的动力越来越大。这些元素，特别是主族金属，传统上被忽视;人们认为它们与无处不在的后过渡金属相比几乎没有用处。现在很明显，情况并非如此，地球上丰富的金属如Al和Ti（它们是地球上第三和第九丰富的元素）具有丰富的催化化学作用，等待被开发。在这个项目中，我将为小分子催化，串联过程准备一系列离散的均相系统，并研究最有前途的系统到二氧化硅的后续异质化。两个选择的（但不限于）实例包括氢化胺化/还原和氢化膦酰化。氢化胺化是在C-C不饱和键上直接加成N-H键，提供了制备含氮底物的原子有效策略。目前，这些都局限于一个狭窄的底物范围，这与选择（或缺乏）可用的催化剂。在该项目的这一部分中，我们将评估基于salalen，salan，脲酸盐，胍酸盐或三嗪酸盐的一系列Ti（IV）和Zr（IV）络合物的底物范围（分子间和分子内氢胺化）。这些将允许一系列的空间/电子效应被探测，以确定结构-活性-relationships.Hydrophosphonylation是一个膦酰基基团和一个氢原子直接添加到C-C不饱和键。这使得能够生产光学活性的-羟基和-氨基膦酸，这是制药工业的一类重要化合物。在这个项目中，我将制备一系列的铝配合物，这是积极的这种转化，基于类似的配体上述加氢胺化。一旦成功的均相催化剂已经开发出来，这些将被拴到SiO2的多相催化，以评估系统的可回收性和比较的选择性，均相情况。将使用文献策略简单地连接配体。最后，我们还将研究并行串联催化在同一个锅中进行多个转换。为此，我们需要匹配催化剂的稳定性，并深入了解反应动力学。

The future of sustainable chemical processes is dependent on a secure supply of catalysts. Since most catalysts rely on platinum group metals (PGMs), which are rare, expensive, and toxic, there is an increasing impetus to develop alternatives. These elements, especially main-group metals, have traditionally been overlooked; it has been assumed that they have little utility compared to the ubiquitous late-transition metals. It is now apparent that this is not the case, and Earth abundant metals such as Al and Ti (which are the 3rd and 9th most abundant elements on Earth) have a wealth of catalytic chemistry that is waiting to be exploited. In this project, I will prepare a range of discrete homogeneous systems for small molecular catalysis, tandem processes and investigate the subsequent heterogenisation of the most promising systems to silica. Two selected (although not limited) examples include hydroamination/reduction and hydrophosphonylation.Hydroamination is the direct addition of an N-H bond across a C-C unsaturated bond providing an atom efficient strategy to prepare nitrogen containing substrates. Currently, these are limited to a narrow substrate scope which are related to the choices (or lack) of available catalysts. In this part of the project we will assess the substrate scope (both inter and intramolecular hydroaminations) with a range of Ti(IV) and Zr(IV) complexes based on salalen, salan, ureates, guanidinates or triazinides. These will allow a range of steric/electronic effects to be probed to ascertain structure-activity-relationships.Hydrophosphonylation is the direct addition of a phosphonyl group and a hydrogen atom across a C-C unsaturated bond. This enables the production of optically active -hydroxy and -amino phosphonic acids, an important class of compounds for the pharmaceutical industry. In this project I will prepare a series of Al complexes that are active for this transformation, based on similar ligands mentioned above in hydroamination.Once successful homogeneous catalysts have been developed, these will be tethered to SiO2 for heterogeneous catalysis, with a view to assess the recyclability of the system and compare the selectivity to the homogeneous case. The ligands will be simply attached using literature strategies. Finally, we will also investigate concurrent tandem catalysis to perform more than one transformation in the same pot. For this we will need to match the stability of the catalysts and have an in-depth understanding of the reaction kinetics.